What Protocol Does Traceroute Use

Traceroute Command

Scanning

James Wide , Andrew Bindner , in Hacking with Kali, 2014

Traceroute

Traceroute uses ICMP's Ping command to find out how many different devices are between the calculator initiating the traceroute and the target. This command works by manipulating the packets time to live value or TTL. The TTL is the number of times the bundle can exist rebroadcast by the next host encountered on the network or hops. The command will outset with a TTL value of 1 indicating the parcel can only go as far equally the next device between the initiator and the target. The receiving device volition send dorsum an ICMP type xi, code 0 parcel (fourth dimension exceeded), and the package is logged. The sender increases the TTL by 1 and sends the adjacent series of packets. The packets will reach their expected time to alive at the next hop along the network; which in turn, causes the receiving router to send another fourth dimension exceeded reply. This continues until the target is reached, and all hops along the manner have been recorded, creating a listing of all devices between the initiating computer and the target. This can be helpful for a penetration tester when determining what devices are on a network. Windows platforms accept a default TTL of 128, Linux platforms start with a TTL of 64, and Cisco networking devices accept a whopPing TTL of 255.

The traceroute command in Windows is tracert . On a Linux organization, like Kali, the command is traceroute . A typical tracert on a Windows car would look like the following.

tracert www.google.com

Tracing road to www.google.com [74.125.227.179]

over a maximum of xxx hops:

1 1 ms <1 ms 1 ms 192.168.1.1

two 7 ms half-dozen ms 6 ms 10.10.1.2

3 7 ms 8 ms 7 ms 10.ten.1.45

4 nine ms 8 ms viii ms 10.10.25.45

5 ix ms 10 ms nine ms x.10.85.99

half-dozen 11 ms 51 ms 10 ms ten.10.64.two

7 11 ms 10 ms 10 ms x.ten.5.88

8 11 ms ten ms xi ms 216.239.46.248

9 12 ms 12 ms 12 ms 72.14.236.98

10 18 ms 18 ms xviii ms 66.249.95.231

xi 25 ms 24 ms 24 ms 216.239.48.iv

12 48 ms 46 ms 46 ms 72.xiv.237.213

xiii l ms 50 ms 50 ms 72.fourteen.237.214

14 48 ms 48 ms 48 ms 64.233.174.137

15 47 ms 47 ms 46 ms dfw06s32-in-f19.1e100.cyberspace [74.125.227.179]

Trace complete.

Many of the scanning tools on Kali make utilize of protocols like TCP, UDP, and ICMP to map out target networks. The consequence of successful scanning phase is a list of hosts, IP addresses, operating systems, and services. Some scanning tools tin can besides uncover vulnerabilities and user details. These details volition greatly enhance the exploitation phase as attacks in this phase can be better targeted at specific hosts, technologies, or vulnerabilities.

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Domain four: Communication and Network Security (Designing and Protecting Network Security)

Eric Conrad , ... Joshua Feldman , in CISSP Study Guide (Tertiary Edition), 2016

Traceroute

The traceroute command uses ICMP Fourth dimension Exceeded letters to trace a network route. Every bit discussed during IP, the Time to Live field is used to avoid routing loops: every time a packet passes through a router, the router decrements the TTL field. If the TTL reaches zero, the router drops the packet and sends an ICMP Fourth dimension Exceeded message to the original sender.

Traceroute takes advantage of this TTL feature in a clever way. Assume a client is iv hops away from a server: the client's traceroute customer sends a parcel to the server with a TTL of ane. The router A decrements the TTL to 0, drops the parcel, and sends an ICMP Time Exceeded message to the client. Router A is now identified.

The client then sends a parcel with a TTL of 2 to the server. Router A decrements the TTL to 1 and passes the packet to router B. Router B decrements the TTL to 0, drops information technology, and sends an ICMP Time Exceeded message to the customer. Router B is now identified. This procedure continues until the server is reached, equally shown in Figure five.ten, identifying all routers along the route.

Most traceroute clients (such as UNIX and Cisco) transport UDP packets outbound. The outbound packets volition exist dropped, so the protocol does non thing. The Windows tracert customer sends ICMP packets outbound; Figure 5.eleven shows Windows tracert output for a route to world wide web.syngress.com. Both customer types usually send three packets for each hop (the three "ms" columns in the Figure 5.11 output).

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Performance Tuning

Kelly C. Bourne , in Application Administrators Handbook, 2014

17.2.4.two traceroute

The UNIX/Linux traceroute command (tracert on a Windows calculator) identifies the route a package takes between your computer and the destination reckoner specified in the command. Every bit a dominion, you lot have very little or no control on how a package gets from betoken A to indicate B. What traceroute offers beyond the ping command is that it lists every hop along the path between the ii computers. This can help you identify if communications are taking besides many hops in the wrong management or whether certain nodes are out of commission. Figure 17.xi shows the output from a traceroute control.

As with many troubleshooting and tuning operations, it is a good thought to use the traceroute command when the network is functioning properly. This volition requite you a skillful thought of what the road, the number of hops taken, and the overall times are like when atmospheric condition are normal. This volition provide you with a basis for comparison so when things aren't working properly you'll recognize the difference.

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Network Troubleshooting

Naomi J. Alpern , Robert J. Shimonski , in Eleventh Hour Network+, 2010

Troubleshooting the Network Layer

When troubleshooting the network layer, you lot'll be most concerned with routers and TCP/IP addressing.

■

Troubleshooting routers

■: Check for configuration errors or misconfiguration issues on each router
■: Bank check for a routing loop by using the tracert or traceroute control
■: Verify that a route exists to the destination network
■: Check for connectivity issues between the source and destination networks, where either a router or a network link that's required has failed or gone offline.

■

Troubleshooting TCP/IP addressing

■: Use the ipconfig command to verify that the IP address, subnet mask and default gateway, and other settings take been configuredcorrectly
■: Use the route command to verify that the default gateway and other routing tabular array entries are correct for an private PC.

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Network Reporting and Troubleshooting

Eric Seagren , in Secure Your Network for Free, 2007

Tracetcp

Oftentimes, the ability to know the path that network traffic is traversing is cardinal to troubleshooting connectivity issues. In most cases you can determine this by using the traceroute utility (tracert on Windows systems). When you execute the traceroute command ICMP (Internet Control Message Protocol) is used to transmit packets to the destination with a Time to Live (TTL) value of 1, and this increases for each hop. When everything goes smoothly, each hop has to reduce the TTL by one, and when it becomes zero, the packet is dropped, and a message is sent to the receiver. The problem that often arises is that ICMP is ofttimes partially or completely filtered out by intervening routers or firewalls. In this case, you demand a way to accomplish the same thing with a protocol that has a higher run a risk of success.

In these cases, a TCP traceroute can exist a life saver. It will finer practice the aforementioned matter, by manipulating the TTL values, but it uses a TCP packet and allows a user-configurable port, which near every firewall and router will allow if it is a well-chosen port. Every bit an instance, if you picked a popular Spider web site and tried a trace route, you may go several instances of "request timed out," which indicates that the hop is not responding. In most cases this ways that ICMP is being filtered by a firewall. If you instead use a TCP-based traceroute utility and specify a destination port of eighty, you may go amend results. A good TCP-based traceroute utility for Windows is tracetcp from http://tracetcp.sourceforge.net/. For Linux, a very robust utility is LFT, which stands for "layer iv traceroute," which can be downloaded from http://pwhois.org/lft/.

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Configuring Cisco Routers

Dale Liu , ... Luigi DiGrande , in Cisco CCNA/CCENT Examination 640-802, 640-822, 640-816 Preparation Kit, 2009

Troubleshooting Routers

Hopefully, once y'all ready upwards a router, you won't have whatever more problems with it. But usually, this is not the example. Sometimes, yous will have problems during the initial setup or after the router has been running for a while. It's important that you empathize that some of the methods tin can assist you in troubleshooting common problems.

Troubleshooting Connectedness Problems

Routers are basically used to connect multiple networks. Sometimes the router itself may exist online but you lot will experience connection problems. The router may non exist able to communicate with various networks or devices. Cisco offers a few User Exec level commands to troubleshoot these connection bug.

■: PING – You lot tin can use the PING command to transport examination packets to a detail device. If you get a response back, y'all know in that location is a concrete connectedness betwixt the two devices. If no response is returned, this could betoken a problem with the physical connection.
■: Traceroute – The traceroute control is used to determine the path between two connections. Often a connexion to another device will have to become through multiple routers. The traceroute control will return the names or IP addresses of all the routers between two devices. This also allows you lot to run across where a packet may exist misguided.

Solving Boot Problems

A less common, only more serious gear up of problems revolve around booting the router. If the router does not boot properly, it is basically useless. It is critical that administrators understand what tin can be done if their router does not kick properly. Therefore, it's likewise critical that you understand this for the examination.

The Configuration Register

Cisco devices contain what is chosen a configuration register, which is a 16-scrap register that controls router behavior. You can use this to control the terminal baud rate and control broadcast addresses. But, what nosotros are nigh concerned with is the fact that changing the value of the configuration can alter how the router boots. This can be a very useful tool in solving boot problems.

The first thing yous demand to know is how to enter read-only memory (ROM) Monitor mode, which allows you to manually manipulate files and the configuration on the router without fully booting the router. You tin enter ROM Monitor mode by pressing Ctrl-Break as the router is booting, or setting the configuration to 2100. To do this, enter the following control:

If you are truly in ROM Monitor fashion, the IOS prompt will appear as rommon 1> on new routers, simply just > on older routers. Once you are in ROM Monitor mode, you can begin manipulating the router files and router configuration.

There are several other useful configuration register settings. Table 4.1 includes a listing of some of the most normally used ones.

Tabular array iv.1. Cisco Configuration Register Settings

Setting	Meaning
0x2101	Load IOS from ROM
0x2100	Kick to ROM Monitor mode
0x2102	Default setting
0x2142	Ignore config in NVRAM on boot

Booting to a Different IOS Epitome

In some situations, your router may non boot properly because of the IOS. The IOS could have become decadent for some reason. Or there may have been a problem trying to upgrade your IOS image. To assistance with this trouble, Cisco devices volition allow yous to kick using a different OS. Two common options to boot include using a different IOS image located in flash or using an IOS image on a TFTP server.

To boot from a different IOS located in flash, type the following in ROM Monitor mode:

Kick system flash ios-prototype-name

To boot from an IOS image located on a TFTP server, blazon the following in ROM Monitor way:

Boot system tftp ios-image-proper name tfp-server-accost

Resetting the Router Password

Occasionally y'all may run into a situation where you will have to reset the countersign of your router. This may be considering you have forgotten the password, or the password was changed by someone else and you lot do not know the new password. As long equally you have concrete access to the router, you can reset its countersign. It's very easy to do, although it does require a number of steps.

EXERCISE iv.3

Resetting Your Router Countersign

Here we volition be resetting your router password. We will first bypass your startup configuration and so make the changes.

ane.: Connect to your router via the console cable.
2.: Power off your router.
3.: Power your router back on.
four.: Utilize Ctrl-Intermission to interrupt the kick sequence. You are now in ROM monitor mode.
five.: Type confreg 0x2142 at the prompt. This turns on fleck 6, which will crusade the NVRAM config to exist ignored.
6.: Reload the router.
7.: Enter privileged fashion.
8.: Enter Global Configuration mode.
9.: Copy the startup config to the running config, using

copy start run

x.: Alter the router passwords.
11.: Blazon confreg 0x2102 to change the configuration register back to normal.
12.: Save the electric current configuration to NVRAM.
thirteen.: Reload the router.

Firmware Upgrade

The firmware running on your Cisco device is the Cisco IOS. At that place volition come a time when you volition demand to upgrade this firmware. This may be necessary in guild to get bug fixes or to enable new router features.

The Cisco IOS is basically a file that gets loaded at device initialization. If you want to upgrade your IOS, you simply have to replace this file with a newer file. Cisco developed the Cisco IFS (Cisco IOS File System), to help you manage files on your router. Yous tin can employ the Cisco IFS to copy the new IOS image to your router.

Practise 4.four

Upgrade Your Router Firmware

Here we will be upgrading your router firmware. This requires us to access the wink memory in your router.

one.: At the IOS prompt, blazon dir . This will list out the contents of your flash retentiveness.
2.: Type re-create tftp://<ipaddress>//ios-image-proper name wink:/ios-image-name
three.: Confirm the source filename. Printing Enter.
4.: Confirm the destination filename. Printing Enter.
5.: Type sh file information wink:ios-image-proper name to verify the new image was copied and is runnable.
6.: Reload the router.

CONFIGURING AND IMPLEMENTING…

Deleting the electric current IOS image

Flash retentiveness on your Cisco router is limited. Sometimes, to copy a new IOS to your router, you have to delete the current IOS from flash. This is done using the delete command. Type delete flash:IOS-Image-Name at the IOS prompt.

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ISE CLI

Andy Richter , Jeremy Wood , in Practical Deployment of Cisco Identity Services Engine (ISE), 2016

Other tools

1 of the more than basic but helpful commands is "nslookup." DNS resolution is of import for ISE so you can apply this to check for normal A/PTR records simply also for SRV records for something like Advertisement by running "nslookup _ldap._tcp.lab.local querytype SRV." You have multiple DNS servers configured; you can also append "proper name-server 〈ip〉" to the stop of the "nslookup" to target specific servers so that yous tin can pinpoint if i of them is returning incorrect information and causing random problems. The "ping" and "traceroute" commands are also useful for ensuring you can correctly connect between nodes.

This adjacent one might exist a bit disruptive and it'southward the "patch" control, which is used to install patch releases onto ISE. The disruptive part here is that you should not use this command from the CLI unless you have very adept reason to. The proper manner to patch nodes is through the spider web UI, where you can upload the patch and ISE takes care of copying the code out to the nodes, installing the patch, and so rebooting the nodes in a sequential order so that your cluster stays in a functioning state while it's happening. The CLI "patch" command on the other mitt merely applies the patch to the one node you are currently on, a nonideal situation in most cases. If you are installing a patch, you probably want it everywhere. Then when will you use this control? You tin use this if y'all take to rebuild a node from scratch and need to bring information technology upward to the same patch level every bit the rest of the cluster before yous join it back. You lot might also want to use this if you lot desire deterministic control over which nodes get a patch practical and when. The web UI volition make certain that you never take all of your PSNs down at the same time but if yous are a global company you will probably want to brand certain that your PSNs are offline during maintenance windows for specific time zones. In that case yous volition need to manually install patches.

Telnet is provided by the CLI likewise and while normally y'all should stay away from anything cleartext for running commands "telnet" hither volition actually give us a simple fashion to check (some) connectivity between nodes or even to other services such as Ad. This image shows us some results.

You tin see nosotros are running the commands "telnet 〈host〉 port 〈port〉" in social club to do this. In the showtime endeavour we connect to port eighty which has an Apache web server listening and we tin run into that telnet connected and basically waited for u.s.. Depending on the remote port you are testing it may human activity different but what'south important here is the fact information technology did connect, which means we have established from our ISE node to the remote node/server the path is clear. The adjacent ii connections show the other possible (common) outcomes when testing ports with telnet. In both cases the ports tin can't connect so we know something is wrong; in the first example in that location is nothing listening on the port used. If you lot were running this test against another ISE node, y'all might get that error if the ISE services hadn't started yet. In the second endeavor we used iptables to replicate what yous would run into with a host behind a firewall/ACL; you volition observe the connection wasn't refused but rather telnet gave up connecting after a period of time.

It'south normally not recommended just the commands nether the "tech" commands tin be helpful for people who have *nix experience and are familiar with top/iostat/vmstat. The nice affair nigh these commands is that the restricted shell just passes the output back to yous without formatting/changing information technology so you get a more than "raw" view of what's going on. The only control here you should probably avoid is "tech dumptcp" which outputs packets from a selected interface. In reality it's just running tcpdump but you can control merely how many packets, if any, are captured earlier the command exits. Without whatsoever power to filter packets you will, on anything other than a small-scale lab deployment, be overrun with packets for clients or only normal traffic and miss what y'all are looking for. If there is a need to debug network communication, it's best to work with TAC and get the root patch installed and then you have direct access to tcpdump.

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Agreement the Methods and Mindset of the Attacker

Dale Liu , in Cisco Router and Switch Forensics, 2009

Nmap

Nmap is a network scanning tool that is gaining in popularity in computer defense and security. Just about anybody who performs network vulnerability assessments or plays a role in computer/IT security has not simply heard of Nmap, only too has used it in one course or another. What used to be a scanning application used merely inside a command-line surround is now incorporated into other network scanning tools and has graphical front ends for ease of utilize.

Nmap is an open up source production, just it was adult through the efforts of Gordon "Fyodor" Lyon, who wrote the original form of this network mapper. Nmap has since revolutionized the world of network security and figurer defence. I of its major features is its power to be customized for a multifariousness of purposes and tasks. For instance, it tin can browse in one configuration one moment, and and so, with a few uncomplicated keystrokes, you tin can customize it to piece of work in an entirely different mode. Although Nmap has a ton of features, it has a bit of a learning curve for people who have had little experience with network scanning and reconnaissance. The original version of Nmap was command-line interface (CLI) driven, so yous had to blazon in the commands, switches, and flags to start a scanning event. But Nmap was ported out to other platforms, including Microsoft Windows, and a GUI version became available.

If CLI entry of commands isn't for you, yous have a few options. If you are working on a Windows PC, Nmap is available with a GUI front terminate that requires that you lot but fill in some blanks and check some options to ready up the application.

If yous are running a Linux system, you may desire to wait into the NmapFE or Zenmap package (I am referring to .rpm packages for Fedora Linux fans and .deb packages for those using Knoppix or Ubuntu/Kubuntu). Information technology'due south the same betoken-and-click process as the Windows version, just within the Linux surroundings.

As just noted, Nmap is capable of performing several tricks, but it takes some effort to learn how to use all of its features. Some of its features include a choice of scanning method, timing options, proper name resolution, spoofing and decoy functions, and various output methods. Figure 7.2 shows several runs of Nmap on a range of network addresses.

Earlier nosotros discuss some of the scanning style selections that yous tin can make with Nmap, you should make sure you understand bones networking fundamentals such as TCP flags, connexion versus connectionless protocols, and other technical terms. You may desire to consult the certificate on Cisco'due south Web site at http://www.cisco.com/en/US/docs/internetworking/technology/handbook/Net-Protocols.html for a refresher. I also recommend yous look at this It Security Basics commodity that is maintained in the SANS Reading Room. It covers good security information especially on the subject of DOS and MitM attacks: http://www.sans.org/reading_room/whitepapers/basics/information_security_primer_443?show=443.php&cat=basics.

Nmap can scan both hosts and networks in a diverseness of ways. You can configure sure controls, such equally speed and aggressiveness, via CLI or through a front end. For instance, Nmap incorporates six different timing templates. You refer to the templates using the –T switch, and they work to govern the menstruation of Nmap packets downwards range to their target. The range goes from five minutes per probe packet (T0) to five milliseconds (T5) per probe packet, so you have a not bad bargain of control over how chop-chop a scan is kicked off and how much noise it makes to the intrusion detection system/intrusion prevention systems (IDS/IPS) keeping sentry over the network. This is to allow someone who wants to run his scan slowly so that he can avoid detection. This flexibility sets them apart from the crazies among us who like to saturate the network with our Nmap probes. Scanning the network too quickly also makes those crazies liable to be detected much quicker as a direct issue.

Nmap is besides capable of scanning hosts in a number of ways to meet certain requirements and circumstances. Nmap can browse its target hosts using Manual Control Protocol (TCP) packets, User Datagram Protocol (UDP) packets, IP packets, and other configurations. When information technology comes to TCP probe packets, Nmap tin can form the packets with specific TCP flags set, such as the SYN, RST, ACK, FIN, URG, and PSH, in whatever configuration suits your fancy. The reason for this is that some firewalls or access control lists (ACLs) are set up to inspect the contents of the flags and make their decision to pass, driblet, or reject based on certain criteria. 1 particular Nmap scan configuration is chosen XMAS because the FIN, PSH, and URG flags are ready (brightly lit, like a Christmas tree), and this may or may not escape package inspection. Some IDSs will fundamental in on this every bit they may have a configured detection signature that triggers on seeing this combination; this is called an NMAP XMAS-Tree scan. Just this, as well, tin can be avoided by setting a flag override.

Once when I was at a former work site, I was informed (and disappointed to learn) that the network security staff decided to limit the rest of the staff'due south ability to troubleshoot network connectivity by blocking Cyberspace Control Message Protocol (ICMP) ping traffic in and out of the routers throughout the campus network. So, i twenty-four hour period the traceroutes would no longer work as the policy was enforced. Yet, on a particularly hot day, I discovered that when I second-naturedly typed in a traceroute command on an Apple Mac running OS 10, I found that it was working across the subnets and all over the network. Every bit it turns out, the security admin had overlooked the fact that Windows systems use UDP packets for their tracert command, but OS 10 pushes out ICMP packets, and they were being overlooked. My colleagues and I became highly interested in what else we could pass.

The moral of this story is to ensure that your policy works as expected in all forms, from soup to nuts. If y'all fail to completely battle-examination your new ACL or your firewall rule, someone like your boss is going ruin your twenty-four hour period and you may take some difficult questions to respond in the event of a horrendous compromise.

Another of import characteristic of Nmap is its power to scan ports and tell yous all sorts of things about the host that maintains them. Nmap can non only scan any of the 65,536 ports on a host, but it tin can also derive certain information from them. Recollect that ports are usually in one of several states: open (accepting connections), airtight (every bit in closed for business), and filtered (which may be another way of saying "firewalled"). In some cases, a port may be reported every bit unfiltered, meaning that Nmap cannot determine whether it is filtered, and is not completely certain information technology is open to make connections. Not only can Nmap written report on this, but it tin easily become further and determine what type of operating system controls the network services on the target hosts. Different operating systems have dissimilar responses to certain network events, and past closely examining the subtle timing differences and responses returned to its probes, an Nmap process can make a decent, intelligent conclusion of the operating organization information technology is probing. Nmap tin can go even further and perform service detection on ports. How many times have you heard someone say that he was going to hide network service by putting it on a not-standard, not-so-well-known port in an effort the reduce attacks to his system? Well, Nmap is capable of detecting whether someone has tried this past setting a Secure Crush (SSH) server to run on port 53 as information technology knows the differences between SSH and domain name system (DNS) servers.

Tons of techs I run into are thrilled with Nmap's Bone detection characteristic (available by invoking the –O switch). Well, Nmap also offers a service fingerprinting characteristic (available past invoking the –sV switch). This can assist to confirm the OS detection results equally well as requite you insight into the precise services that are running on the organisation.

Nmap is also known for its output and reporting features. The software tin can give you lot its scan results in a variety of ways. Every bit you saw in Figure 7.two, each port condition appears on a line by itself, and normally that is okay for a visual display. Merely when you are scanning dozens to thousands of hosts, you lot will not want to look at this information line by line when you can run the results through a text-searching tool to categorize the results. Toward that end, Nmap is able to likewise dump its results to an XML-formatted file, or to a file you can search using a grep control (or whatever you lot like that is capable of running regular expression searches/filtering). Nmap too offers the option of putting the results in all iii formats if y'all want, and all you have to do is provide a base filename in the control before yous kick off the browse.

Notes from the Underground…

So, Do You Really Recollect You Know Who Is Scanning You lot?

Are you lot interested in knowing how adept penetration testers keep their addresses hidden for as long as possible? Information technology'due south a matter of hiding amidst the other IP addresses which are nowadays, and spoofing an IP accost. Two absurd ways that you tin can obfuscate your IP accost every bit the source of scanning activity involve using the decoys role and spoofing your Media Admission Control (MAC) address.

Here we have called to designate a few extra decoys along with our scan to make the scans appear as though they are coming from a number of systems, rather than just ours. (Call up the age-old rule of safety in numbers!)

Here is an example of this technique sending ACK flags to port 80 at Captain Insaneo-speed:

#nmap –n –PA –p eighty –T5 –D ten.ane.1.1,x.one.2.one,66.i.2.half dozen,ME,202.3.192.1 <target>

As far every bit MAC address spoofing is concerned, today it is easy to spoof the source MAC address of the interface Nmap is using, and you lot don't even have to look information technology up. Say, for instance, that you visit an fine art studio with an Alienware system as your vulnerability cess calculator, and all your targets are Macintosh systems. If you run an Nmap browse without making a change to obscure your organisation'due south identity, your system is going to stick out like a sore thumb. Then, you conjure upwardly some "lucky charms" and utilize a detail MAC address vendor—and throw the security officer for a loop every bit he goes around looking for an HP Compaq organization. Here is the Nmap command yous would laissez passer in this instance:

#nmap –due north –PA –p 870 –T5 –spoof-mac HP <target>

If yous wanted him to call back that a Linksys router was involved, endeavor this:

#nmap –north –PA –p 870 –T5 –spoof-mac Linksys <target>

Good times!

Although we talked about only a handful of features, Nmap has numerous others that we don't take the space to cover. Suffice it to say that Nmap has made a huge affect on computer security and organization administration and about likely will proceed to practise and then as information technology continues to be developed through open source participation from around the earth.

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UNIX Tools

Kelly C. Bourne , in Application Administrators Handbook, 2014

24.10 Connectivity

More than than probable your awarding server doesn't be in a vacuum. The awarding might consist of multiple servers, e.thousand., a spider web server, a report server, etc. The application might exist in a load-counterbalanced surround. It might utilize a cluster to improve either operation or availability. The database very likely resides on a dissever, dedicated server.

If any of the above situations be in your environs, and so you're going to exist dealing with multiple servers. Multiple servers means that you'll have to understand how to communications between those servers occurs. The tools or commands listed in this section tin can provide insight into communications betwixt servers or between your server and the larger world.

As an Application Ambassador mayhap your most troublesome problems will be dealing with potential connectivity issues. When hunting down connectivity issues information technology'due south helpful to have a checklist of things to check and always run through them in social club. Afterwards a while you'll go a feel for what's causing the consequence this time. Some examples of typical connectivity-related problems include the post-obit:

•: Is the application server experiencing issues connecting to the database server?
•: If the application is running on multiple servers, e.yard., an application server and a reports server, are they able to connect to each other?
•: Are users having issues connecting to the application server?
•: Are users able to connect to the system'due south network?
•: Tin can users access the organization'south network from a remote location?
•: Are performance problems experienced by users being caused by the awarding, the database, the network, or something else?

To troubleshoot problems like the ones listed in a higher place you need to know what tools are available on your server. Every organisation'southward environment is different, but the tools that are described in the following sections are probably available on your UNIX server. The sections are organized from the simplest check first and the about complicated checks last.

24.10.1 ping

The ping command was described in Chapter 23. Information technology works essentially the same under Windows and UNIX. Enter "ping" and some other reckoner's proper noun or IP address. The format of both ping commands is shown here. Ping will decide if the destination is reachable. If ping continues to display output lines you can printing Ctrl-C to impale it:

ping computer-name

ping IP-address

If you become an mistake bulletin saying the ping command is not institute and then attempt entering ping as follows:

/usr/sbin/ping reckoner-name

At that place are ii potential shortcomings to using the ping command. The first is that if you enter the name of the remote computer it'southward possible that your DNS (Domain Proper noun Organisation) server is translating the server name you entered to the wrong IP address. If an inaccurate IP accost is being provided, this could be the source of your problem. To determine whether or not this might be the problem you lot should compare the IP accost returned by a "ping computer-proper name" command with your documentation that identifies the IP address of the remote computer. If the IP address returned by the ping-by-name doesn't match your records, then a trouble exists in the DNS area. Contact your network squad and piece of work with them while they resolve information technology.

You should also execute a ping command and specify the IP address of the remote reckoner. This volition help you determine whether the remote figurer can be accessed if an accurate IP accost is being used.

The previous advice assumes that you have a "mural" certificate or other documentation that shows the name and correct IP address for all of the organization's computers. If this documentation doesn't be, and then at present would exist a very good time to create it.

The second potential trouble with a ping command is that some servers have been configured to ignore ping commands. This is done equally a security measure out to help protect them from DOS (denial of service) attacks. If you lot go the effect "Request Timed Out" every time y'all ping a particular server, so this probably means it has been ready to ignore ping commands.

24.ten.2 Database connectivity

If your connectivity problem appears to be related to the database, then you should come across if the database server can be accessed from the application server. At that place may be a tool on the application server that enables you to initiate a database session. For example, if the database beingness used is Oracle, and then SQL*Plus has likely been loaded onto the application server. Open a SQL*Plus session with the database using a command like the following:

sqlplus username/[email protected]

If the session established, it proves that connectivity with the database server exists. If the SQL*Plus command fails, and so a problem exists. The next pace would be to work with the DBA squad to confirm that the database engine is running. If information technology is, then y'all might need to work with the network team to verify that the awarding server can communicate with the database server.

24.10.iii Traceroute

If the ping-past-name and the ping-by-IP were unsuccessful, then yous demand to detect out where along the path between your server and the destination it failed. You need to know if your computer is able to communicate with the Internet or other networks. Your arrangement has a device chosen a gateway router that acts as a gateway between your network and all other networks. Run the "traceroute" command to determine whether your communication attempts are getting out the door and then to speak. If the results indicate that your traceroute endeavor didn't go far past your gateway router, then you need to contact your organization's network team to resolve the trouble.

traceroute, like ping, confirms whether or not connectivity to the destination calculator can be established. The output from traceroute indicates how many servers or hops it takes a packet to get from your server to the destination computer. The format of the traceroute command is:

traceroute destination

where destination tin be either a name or an IP accost.

This control can exist very informative if communications with another computer are extremely ho-hum. Information technology can tell you lot either that the packets are taking an excessive number of hops taken forth the path or that a specific computer in the path is taking longer than expected to communicate. If either of these is the case these, the problem isn't with your server.

24.10.4 tnsping

tnsping is a utility provided by Oracle that determines if connectivity to the Oracle database server can exist established. If your application uses an Oracle database, then you can use tnsping to determine if the application server can communicate with the Oracle database server. The format of the command is:

tnsping service-name

If yous don't know the value of the service proper noun yous can observe it in the tnsnames.ora file within the Oracle Client software subdirectory.

24.10.5 netstat

netstat displays the post-obit network communications related information:

•: Agile ports—running netstat with the—an choice displays a list of all active ports. This ways a listing of incoming and approachable network connections that are currently open on the server. It also lists the process that opened each port, whether the port is open for input or output and what protocol is being used.
•: Routing tables—the routing table holds the list of computers that can be direct communicated with. It might be a surprise to y'all, only your server isn't aware of every server on the Internet. It is aware of a few other computers which are aware of a few more than computers which are enlightened of still more computers, etc. To view only routing table information include the –r option when calling netstat.
•: Statistics by protocol can exist obtained by running netstat with the –south option displays a list of statistics for each of the protocols (tcp, udp, ip, icmp, igmp) that are supported. Some of the stats that are displayed are: packets sent, packets received, connectedness requests, connection accepts, connections established, and timeouts.

24.10.6 ruptime

ruptime, remote uptime, shows the condition of all machines on the network. It likewise provides information on how long each calculator has been up and what its contempo load level is. The germination of ruptime is as follows:

ruptime

24.10.7 rwho

rwho, remote who, lists who is logged onto all machines in network. Exist aware that rwho isn't available on all networks due to security concerns. If you need to know who is logged into some other figurer and "rwho" doesn't work, and so you'll have to remote to that auto and run "who" on information technology. The format of this control is:

rwho

24.ten.8 nslookup

If your users or awarding is no longer able to connect to a server, the problem could be that the local name server has out of date or otherwise inaccurate information. The nslookup command allows you to query the Domain Name System (DNS) to gather information on domain names information technology contains. Using it you tin can learn the proper noun and IP address of the name server that is beingness used. Yous can also obtain the IP addresses of machines that the name server is maintaining data on.

Figure 24.viii shows the results of an nslookup call to get the details on server "dr005." The nslookup command has other available parameters which can be seen on the homo page for it.

24.10.9 Firewall problems

It's possible that your organization'due south firewall is causing the connectivity issues. Information technology's not uncommon for a change in a firewall'southward configuration to cause problems connecting to a server that was working just fine yesterday. Depending on your level of expertise yous could investigate this yourself or contact the organization's squad that administers the firewall. A discussion of warning is definitely in guild here: be very careful non to crusade problems or make unapproved changes of the firewall. Doing so could cause extremely serious bug for you, your users, other applications, and their users.

If you're noesis about the organization'south firewall, you lot might consider checking the firewall configuration or its logs to see if in that location are any clues about the trouble. Ii commands that might provide some insight are:

iptables –n –L	Lists all rules configured in the firewall. If you're not familiar with firewall rules, then the output from this command will probably be undecipherable to you.
tail –f /var/log/messages	Repeatedly lists the 10 most recently added entries in the log files located in directory /var/log/letters.

24.x.10 Network assay tools

In that location are a number of network analysis tools that tin can be caused to provide detailed information on the communications betwixt your server and other machines. Providing an in-depth description of whatever of them is beyond the scope of this volume, but a brief description of some tools that are bachelor is provided.

24.ten.10.i tcpdump

tcpdump is a parcel analyzer that is launched from the command line. It can be used to analyze network traffic by intercepting and displaying packets that are being created or received by the computer it's running on. It runs on Linux and nigh UNIX-type operating systems.

24.10.10.2 Wireshark

Wireshark is an open source tool that is used for troubleshooting network bug. It runs on Linux, Windows, and many UNIX-like operating systems. You tin can employ Wireshark to capture all packets on the network, but demand to be careful that the book of traffic being captured doesn't become overwhelming. The GUI (graphical user interface) in Wireshark makes it relatively piece of cake to capture merely the specific traffic that yous're interested in.

24.ten.x.3 Cheops

Cheops is an open source package that provides numerous network-related utilities. Using it you can locate, diagnose, and manage network resource. It tin can place the operating systems of all hosts on the network. It provides a mapping of your network and if information technology's particularly large you tin can break the overall map down into multiple views. A port scanner documents what tcp ports are beingness used.

24.10.11 Connectivity tools

There are a number of connectivity-related tools bachelor in UNIX. They are described in the post-obit sections. Application Administrators should have at least a working knowledge of connectivity tools.

24.10.11.1 Telnet

Telnet is a utility that enables you to remotely connect to another reckoner and open up a concluding session on it. Use of telnet has diminished significantly considering it isn't a secure communication method. If y'all desire to log onto another computer using telnet the format is:

telnet remote_computer.domain.org

You will be prompted for an ID and password to consummate the connexion process. If the computer is on the same network every bit the calculator you are logged into, then y'all can omit the ".domain.org" from the command.

24.x.11.two rsh

Rrsh (remote shell) is another method of remotely connecting to another computer and running a terminal session on it. To use rsh to open a session on a remote figurer, yous must have an account on that computer. When the connexion is established, you'll exist prompted to enter your password. The format for using rsh is:

rsh remote_computer.domain.org

One variation of rsh is that it can exist used to execute just a unmarried command on the remote figurer instead of opening a last session. The format for using rsh in this manner is:

rsh –l username remote_computer.domain.org command

24.x.eleven.3 ssh

ssh (secure shell) is a more secure way to log onto a remote arrangement. ssh offers similar functionality to rsh simply more securely. Communicates passed between computers during an ssh session are encrypted, so they are much better protected than either telnet or rsh. The format of the ssh control to initiate a remote terminal session is:

ssh remote_computer.domain.org

You volition be prompted for the password before the remote session is established.

24.10.11.4 PuTTY

PuTTY is an open source utility that allows you to connect with remote computers. Although it was originally written for Windows it has been ported to a number of UNIX platforms. PuTTY was described in detail in Section 23.5.iv of Chapter 23.

24.x.11.5 ftp

ftp, file transfer protocol, is a UNIX application that is used to transfer files between machines over a network. There are numerous GUI implementations of ftp, only near UNIX systems support the control line version of this tool. To initiate an ftp session enter the post-obit control:

ftp remote_computer.domain.org

You will be prompted for your username and password. Once your ftp session has been established, you can apply whatsoever of the post-obit bones instructions to transfer files to or from the remote computer:

•: cd—change the working directory on the remote reckoner
•: lcd—change the working directory on your local computer
•: mkdir—make a directory on the remote computer
•: ls—list files in the working directory on the remote computer
•: bin—sets the manner so file will exist transferred in binary mode
•: asc—sets the mode so files volition exist transferred in ASCII, i.e., characters, way
•: put—moves a file from the local figurer to the remote computer
•: get—retrieves a file from the remote calculator to the local figurer
•: help—displays a list of available commands and their parameters
•: quit—get out out of the ftp session

24.10.11.6 rcp

rcp, remote copy, is a UNIX command that allows yous to transfer one or more than files to or from a remote computer. In order to motility files to or from another computer, you must already have an agile account on the remote auto.

The format of a basic rcp command to copy a file to a remote computer is:

rcp example.txt [e-mail protected]_computer.domain.org:

The command to copy a file from a remote computer to your local computer is:

rcp [email protected]_computer.domain.org:example.txt

24.10.xi.7 scp

scp, secure copy, has like syntax and functionality as rcp, simply is more than secure. SCP encrypts the contents of the file before transferring it. If someone is capturing and examining the packets in your file transfer they wouldn't be able to read them.

The format of a basic scp command to re-create a file to a remote figurer is:

scp example.txt [email protected]_computer.domain.org:

The command to copy a file from a remote computer to your local computer is:

scp [email protected]_computer.domain.org:instance.txt

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Troubleshooting the Juniper Firewall

Brad Woodberg , ... Ralph Bonnell , in Configuring Juniper Networks NetScreen & SSG Firewalls, 2007

Troubleshooting Tools

The Juniper firewall has several troubleshooting tools built in to it. This section covers these tools in particular. Each has a specific purpose and should cover any troubleshooting needs you have.

Tools & Traps…

Secure Troubleshooting

One matter you want to make sure of when troubleshooting your firewall is that you lot don't compromise your security during the troubleshooting procedure. If you lot're using HTTP (Hypertext Transfer Protocol) or Telnet to access your firewall, someone may exist able to sniff your packets while yous're working to solve the issues.

The WebUI can exist encrypted with SSL (Secure Sockets Layer) or tunneled through a VPN. It is recommended that this connection exist secured at all times. The document can be self-signed by the Juniper firewall, so no certificate has to be purchased.

The control-line interface can be encrypted past using SSH (Secure Vanquish) to log in to your firewall. Telnet should be disabled and so it cannot be used by anyone. If Telnet access is required for some reason, be sure to encrypt the packets using a VPN tunnel. Serial console admission requires physical access to the firewall. You can disable all CLI access if you wish and require series access to manage the box, but this measure out might be a bit extreme.

Ping

Ping is probably the about well-known network troubleshooting utility in existence. The ping control is used to test for network connectivity. Every network operating system has a version of it preinstalled. It was written in December, 1983 past Mike Muuss for BSD Unix. The BSD Unix network stack has been ported to many operating systems, including every version of Microsoft Windows. Although the name was originally derived from a sonar analogy, it is now referred to equally an acronym for Bundle Net Groper.

The functionality is uncomplicated: send an ICMP (Internet Control Message Protocol) echo-asking and wait for an ICMP echo-reply. The code shown in Figure xiii.1 is an instance of sending a ping to IP address 192.168.0.ane, and getting iv replies in return. This is a connectivity cheque from a Windows machine to a router.

By default, the NetScreen device volition send five ICMP echo requests of 100 bytes each with a ii-second timeout. Advanced settings can also be included on the command line:

You may likewise set all of the options manually by entering only the command ping and pressing Enter. At this point, you will exist prompted for each i of the options to build the control you wish to execute, specifying target IP, the number of requests, the datagram size, and so on.

Figure 13.two shows an case of using the ping command in ScreenOS 5.

Keep in mind that the results of the ping control may not always be accurate. Some network traffic does not pass ping traffic and could possibly change the results of the command.

You lot can likewise ping from a specific interface with the ping command ping <ipaddress> from <interfacename> (see Figure thirteen.three)

traceroute

The traceroute command is useful in troubleshooting multihop routing. traceroute uses the TTL (Time to Alive) field of the IP protocol to go an ICMP TIME_EXCEEDED response from each gateway the packet goes through to attain the destination. Effigy 13.iv shows an example of traceroute in ScreenOS.

traceroute results should likewise be taken with a grain of salt. Since traceroute uses TTL fields in the packets, any devices that do not respond to that field will not return valid data.

Get Session

The get session command will show all electric current established sessions going through the Juniper firewall. If an entry exists in the session table, the connection has passed through the routing table and the policy successfully.

Each session entry has three lines of information. The commencement line contains the policy rule number, which can be viewed past the get policy command. The time entry shows idle time and resets every fourth dimension traffic goes through the firewall. Figure 13.5 illustrates these points.

The output from the get session command tin seem a bit overwhelming at first, just it isn't really that bad one time y'all suspension it downwardly. Kickoff, the command specifies how many sessions are currently allocated (in the preceding case, information technology is 64 with a maximum number of 128064). This command also specifies how many sessions failed to be allocated (both regular and DI sessions) and how many multicast sessions are allocated. It as well provides statistics for the retention and sessions pools. The next part of the command that you actually should exist concerned with is the information nigh the source IP address, source port, traffic direction, destination address, and destination port. The first entry in Figure xiii.five is: 218.172.211.178/18772->123.49.20.57/1024. This stands for a source address of 218.172.211.178, with a source port of 18772 going outbound to destination 123.49.twenty.57 port 1024. It will be using route 0, which you can verify with the get route control and compare that confronting the route ID value in the output. Traffic with the <- symbol designates the inbound (render) traffic. The return traffic may also show the NAT'd value of the packet, and the subsequent road which may exist taken to reach the destination. You lot can besides see which policy (in this instance 320000) is existence matched for this session.

Go Policy

The become policy command displays the current NetScreen policy. This command is useful as a reference to see which policy ID is assigned to each rule. Pay attention to the From and To fields. These indicate which zones each policy crosses, as shown in Figure thirteen.6.

Get Road

The get route command shows the current NetScreen routing table. There is a divide routing table for each virtual router. In the case in Figure 13.7, at that place are no routes for the untrust-vr, which is the default configuration. Brand sure you differentiate which routes are static and which are added by a routing protocol.

Remember that the * next to a route designates that information technology is the active route in the routing tabular array, and the ID is the value that is besides referenced in other troubleshooting commands such as the get session command. This output shows you that road 12 is agile over the aforementioned road (unlike side by side hop) route thirteen. They are both Static routes with a preference of 20, and a metric of 1. It is non immediately clear in this case why route 12 is valued college than 13, just the reason could be because ethernet0/1 is physically down.

Get Interface

The get interface command shows detailed interface statistics. This command (shown in Figure 13.8) is useful to run into which zone an interface is in and which hardware MAC (Media Access Control) address is assigned to each interface. You can also see the IP address, VLAN, and what state the interface is currently in (U for Upwards, D for Down.)

Go ARP

The ARP (Address Resolution Protocol) table of the Juniper firewall can be viewed past using the go arp command. This can exist useful when troubleshooting OSI layer ane and layer 2 problems. Figure xiii.9 shows the ARP table of the Juniper firewall.

Nosotros can meet in this example that the MAC address for 218.172.211.177 is invalid (000000000000.) It also specifies what interface this will endeavor to learn the MAC accost on, which volition be whatsoever interface has an IP address in the same subnet as the IP accost that you are ARPing for. This can be very useful to troubleshoot layer 2 bug, particularly when devices are connected directly to your firewall.

TIP

Please remember that if you lot are replacing one network gateway device with some other (such as the SSG), the MAC accost will alter considering at that place will be a new hardware interface in place of the quondam 1 (assuming yous are keeping the aforementioned IP address). This will mean that other devices may not recognize this new MAC address until either their ARP enshroud times out (often 10 minutes on most systems), or you can manually clear information technology, such as issuing the articulate arp on the Juniper firewall, or arp –d on Windows.

Get System

The get organisation command gives you several important pieces of information. Use this command to get an overview of your firewall and the setting for each interface. On an unknown firewall, this should exist the first command y'all use.

▪: Serial Number This tin exist used to reset the device to the manufactory defaults. Use the serial number as the username and password when logging in on the serial interface. Be aware that this will as well wipe out whatever configuration changes you take made. The serial number is used to generate the license keys for your device likewise.
▪: Software Version The software version of the ScreenOS device in running retention.
▪: Date and Time Returns the date and fourth dimension on the NetScreen device.
▪: Total Device Resets Tracks the total number of asset recovery resets. This number counts the number of times the organisation has been reset to the factory defaults.
▪: User Proper name The username of the electric current user.

Debug

The debug utility in ScreenOS is a powerful troubleshooting tool that allows you to track sessions going through the Juniper firewall. The firewall has a memory buffer prepare bated for the debug organisation, and packets can be captured in this memory for inspection. The following outlines various uses of the debug system:

Footstep i.: Gear up whatsoever filters necessary for the debug. This is optional, but information technology might help consolidate the results. Optionally, you might also want to clear the buffer of erstwhile debugs then that you get a better snapshot.
Step 2.: Upshot the Debug Control.
Step 3.: Upshot the get db str command to get the output stored in the memory buffer from the debug.
Stride 4.: Cease the debug with the undebug all command which will halt whatsoever debugs. Alternatively you tin can go along issuing the get db str command to go on getting output from the debug.
Step five.: Clear the memory buffer with the clear db command.

Alarm

You must be mindful that issuing debug commands can increase the load on the firewall. Althought information technology is non equally crippling as debugs on other platforms (historically,) it can cause bug if y'all are not careful. It is best to use flow filters, and turn the debugs off as presently as possible.

Flow Filters

A filter can besides exist put into place to limit what traffic gets sent to the debug buffer. The command set ffilter allows y'all to select the type of traffic to collect. The following filters are bachelor:

▪: dst-ip Destination IP address
▪: dst-port Destination port
▪: ip-proto Internet protocol number
▪: src-ip Source IP accost
▪: src-port Source port

If multiple filters are specified in the gear up ffilter command, the filter will only collect traffic that matches all of the filters specified. The set ffilter control can be executed multiple times, and traffic will exist collected if information technology matches any of the filters. For example, to filter all tcp traffic from 192.168.0.1 to 10.1.1.1, issue the following command:

SSG550-> set ffilter src-ip 192.168.0.1 dst-ip x.1.1.1 ip-proto 6

To view current filters, use the go ffilter command. Each filter in place has an ID number to identify it. To remove a filter, use the unset ffilter command, followed by the ID number of the filter to be deleted.

Snoop

Snoop is a total packet sniffer. The output of snoop goes into the aforementioned retentivity buffer that debug sends to. The biggest difference between debug and snoop is that snoop can dump the bodily contents of the packets to the memory buffer. snoop output is more difficult to read than debug output and is typically used when the contents of the packets need to be analyzed. The following are the commands for using snoop:

▪: snoop Starts the snoop capture.
▪: snoop info Displays current snoop condition.
▪: snoop particular Enables full packet logging. This logs the full contents of the packets.
▪: snoop off Turns off the snoop capture.
▪: snoop filter Allows yous to filter what gets captured. Employs syntax similar to that used for debug filtering.
▪: clear db Clears the debug memory buffer.
▪: become dbuf stream Displays the output for analysis.

Firewall Session Analyzer (FSA)

Juniper has created a new Web-based tool chosen Firewall Session Analyzer (FSA) to assist brand sense of the torrent of information that tin can come from running a get session command. Every bit discussed earlier, this command shows all current established sessions going through the NetScreen device, and this can seem a trivial daunting when viewed in the console.

After uploading a log of the get session control output to the FSA (located at http://tools.juniper.net/fsa/), it will generate the following seven reports.

▪: Rank based on destination IP address
▪: Rank based on destination port
▪: Rank based on source IP address
▪: Rank based on source port
▪: Rank based on protocol
▪: Rank based on Virtual Organisation Device (VSD)
▪: Rank based on source IP with protocol and destination port data

In order to use the tool, y'all need to log the command output to a file on a TFTP server by using the post-obit command.

SSG550-> get session > tftp <server ip> <filename>

You lot may also choose to capture the screen output to a file and upload it to the analyzer in the same manner equally the file stored on the TFTP server. Once you have the log file, generating the FSA reports is simple.

1.: Go to http://tools.juniper.cyberspace/fsa/ using your Web browser.
ii.: Browse to your become session .log or .txt file, starting time making sure the file does not exceed 10MB.
3.: Choose the version of ScreenOS the file was captured from (ScreenOS v4 or v5).
4.: Click Submit. After several seconds, your results volition be viewable in a new screen.

The top 10 results for each of the seven previous reports will be viewable on 1 page (see Figure 13.x), at which point you can download each complete report as an individual csv file by selecting the link for the written report you desire. This information volition be available for you lot to view for one hour following the execution of the analyzer. Later one hour, the information processed past the tool, and the corresponding reports, will be deleted from the Juniper site for security reasons.

Putting Information technology All Together

When troubleshooting the Juniper firewall, use any of the previous commands necessary to resolve the issue. When a bundle arrives at an interface of the firewall, the following things happen.

1.: The packet goes through a "sanity check" to make sure it isn't decadent.
2.: A session lookup is performed. If the packet is part of an existing session, it follows the remainder of the packets in the same session.
3.: The packet is routed, based on the routing tabular array and zones.
4.: The packet is checked against the firewall policy.
5.: The ARP enshroud is referenced.
half-dozen.: A session is created if i does not be, and the packet is forwarded.

Notice that the session is not created until the package passes through the routing tabular array and the firewall policy.

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