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ICMP/PING, Traceroute

ICMP/ PING and Traceroute Literally, ping means a single short ringing sound or beep. But, in an Internet: Packet Internet Groper is Internet Control Message Protocol (ICMP) echo message and its reply; ping often is used in IP networks to test the reachability of a network device. Ping is usually a response time: the length of time, in milliseconds, that it takes to send a message to an intranet, Internet, or web address and receive a reply, Or to check for response from web address: to send a packet of data to an intranet, Internet, or web address to check whether it is accessible or is responding.

ICMP Echo Request One type of ICMP message, created specifically to be used as the message sent by the ping command to test connectivity in a network. The ping command sends these messages to other hosts, expecting the other host to reply with an ICMP Echo Reply message.

ICMP Echo Reply One type of ICMP message, created specifically to be used as the message sent by the ping command to test connectivity in a network. The ping command expects to receive these messages from other hosts, after the ping command first sends an ICMP Echo Request message to the host. Let me show you a ping timeout and a successful request/reply.

Time Out VPCS[1]> ping 10.10.10.1 -c 1 10.10.10.1 icmp_seq=1 timeout

Successful Reply VPCS[1]> ping 10.10.10.1 -c 1 10.10.10.1 icmp_seq=1 ttl=255 time=16.012 ms The results above are copied from CMD on PC where the one below is the ping result copied from CLI of a router. VINA#ping ip 10.10.10.2 repeat 1 Type escape sequence to abort. Sending 1, 100-byte ICMP Echos to 10.10.10.2, timeout is 2 seconds: ! Success rate is 100 percent (1/1), round-trip min/avg/max = 16/16/16 ms

ICMP Captured Packet No Time 24

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Source Destination Pro. 862708000 10.10.10.2 ICMP 10.10.10.1

LNG. Information Echo (ping) request id=0x0004, seq=0/0, 114 ttl=255 (reply in 25)

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ICMP/PING, Traceroute

863691000 Echo (ping) reply id=0x0004, seq=0/0, 10.10.10.1 ICMP 114 10.10.10.2 ttl=64 (request in 24) Before we go and talk about PING in more detail let me first show you how to redirect ICMP. Hopefully, you are a bit familiar with the “no” command in Cisco, aren’t you? Let’s see how to use “no” command with ICMP on a CLI. 25

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Disabling Redirection VINA(config)#interface GigabitEthernet 0/0 VINA(config-if)#no ip ? Interface IP configuration subcommands: redirects Enable sending ICMP Redirect messages VINA(config-if)#no ip redirects What does this command actually do? This command ICMP redirects from this specific interface. If you want to re-enable the ICMP redirection simply do as below:

Enabling Redirections ICMP-PING(config-if)#ip redirects If you want to verify that if your configuration had worked, do as below:

Verifying Configurations VINA(config-if)#do show run | begin GigabitEther interface GigabitEthernet0/0 ip address 10.10.10.1 255.255.255.0 no ip redirects ! You can clearly see the message of “no ip redirects” in the third line of the show command’s output. But, if you’ve already re-enabled the “ip redirects” command the show result would be as the one below: VINA(config-if)#do show run | begin GigabitEther interface GigabitEthernet0/0 ip address 10.10.10.1 255.255.255.0 Now, let’s go for the ping command. Command Explanation VINA#ping A.B.C.D Checks for Layer 3 connectivity with device at address A.B.C.D VINA#ping Enters extended ping mode, which provides more options When you issue the second command (VINA#ping) the CLI asks you a fewer things as below:

Extended ping An IOS command in which the ping command accepts many other options besides just the destination IP address.

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ICMP/PING, Traceroute

VINA#ping Protocol [ip]: ip Target IP address: 10.10.10.2 Repeat count [5]: 1 Datagram size [100]: 37 Timeout in seconds [2]: 1 Extended commands [n]: yes Source address or interface: GigabitEthernet Translating "GigabitEthernet" % Invalid source. Must use same-VRF IP address or full interface name without spaces (e.g. Serial0/1) Source address or interface: GigabitEthernet0/0 Type of service [0]: 1 Set DF bit in IP header? [no]: yes Validate reply data? [no]: yes Data pattern [0xABCD]: Loose, Strict, Record, Timestamp, Verbose[none]: Sweep range of sizes [n]: yes Sweep min size [36]: 36 Sweep max size [18024]: 37 Sweep interval [1]: 1 Type escape sequence to abort. Sending 2, [36..37]-byte ICMP Echos to 10.10.10.2, timeout is 1 seconds: Packet sent with a source address of 10.10.10.1 Packet sent with the DF bit set Reply data will be validated !! Success rate is 100 percent (2/2), round-trip min/avg/max = 4/24/44 ms NOTES: 1. Datagram size [100]: The size shouldn’t be less than 36 or the result will be an error. 2. Source address or interface: Either of the inputs are valid e.g. 10.10.10.2 [IP] or GigabitEthernet0/0 [Interface]. 3. Source address or interface: GigabitEthernet 0/0, will be resulted in an error. 4. Source address or interface: GigabitEthernet, and you hit enter the CLI will look for translator to translate it. Provide the full address without spacing. 5. Sweep min size [36]: 36 is the minimum size. You cannot enter a number less than 36. 6. Sweep max size [18024]: 18024 is the maximum size. You cannot enter a number greater than 18024. If you look at the ping out from a CLI, you’re probably going to see some character, as in our case is “!”, you noticed, didn’t you? VINA#ping 10.10.10.2 repeat 5 Type escape sequence to abort. 3 BY VIRGINEX

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ICMP/PING, Traceroute Sending 5, 100-byte ICMP Echos to 10.10.10.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 8/12/24 ms

What does the character mean? Let’s talk about it! Character Meaning ! Successful receipt of a reply. . Device timed out while waiting for a reply. U A destination unreachable error protocol data unit (PDU) was received. Q Source quench (destination too busy). M Could not fragment. ? Unknown packet type. & Packet lifetime exceeded. NOTE: A host name can also be pinged if resolver is configured. The command would be: VINA#ping vx.

Ping from a PC (Alex) PC>ping -n 1 vina Pinging 10.0.0.1 with 32 bytes of data: Reply from 10.0.0.1: bytes=32 time=0ms TTL=255 Ping statistics for 10.0.0.1: Packets: Sent = 1, Received = 1, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms

Ping from a Router (VINA) VINA#ping vx-server Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 10.0.0.3, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 0/0/0 ms NOTE: If you won’t tell your DNS server that it itself is a DNS it won’t ping the host names, see how:

Before Configuring DNS Address SERVER>ping vina Ping request could not find host vina. Please check the name and try again.

After Configuring DNS Address SERVER>ping -n 1 alex Pinging 10.0.0.2 with 32 bytes of data: Reply from 10.0.0.2: bytes=32 time=0ms TTL=128 Ping statistics for 10.0.0.2: Packets: Sent = 1, Received = 1, Lost = 0 (0% loss), 4 BY VIRGINEX

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ICMP/PING, Traceroute Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms

So, it was all about PING and ICMP. Now, let’s talk about traceroute.

The Traceroute A program available on many systems that traces the path that a packet takes to a destination. It is used mostly to debug routing problems between hosts. No Time

Source Destination 236810000 3 4 10.10.10.2 10.10.10.1 237814000 4 4 10.10.10.1 10.10.10.2 256826000 5 4 10.10.10.2 10.10.10.1 257824000 6 4 10.10.10.1 10.10.10.2 266830000 7 4 10.10.10.2 10.10.10.1 267830000 8 4 10.10.10.1 10.10.10.2 Again, if you’ve DNS server, do as below:

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ICMP 70 UDP

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ICMP 70 UDP

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Information Source port: 49158 Destination port: traceroute Destination unreachable (Port unreachable) Source port: 49159 Destination port: 33435 Destination unreachable (Port unreachable) Source port: 49160 Destination port: 33436 Destination unreachable (Port unreachable)

Tracing a Hostname VINA#traceroute alex Type escape sequence to abort. Tracing the route to 10.0.0.2 1 10.0.0.2 0 msec 1 msec 0 msec Microsoft accepts a command similar to traceroute, see below:

Tracing a Hostname from a Microsoft Machine PC>tracert vina Tracing route to 10.0.0.1 over a maximum of 30 hops: 1 0 ms 0 ms 0 ms 10.0.0.1 Trace complete.

Optional Ping Commands C:\Users\VIRGINEXj>ping Usage: ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS] [-r count] [-s count] [[-j host-list] | [-k host-list]] [-w timeout] [-R] [-S srcaddr] [-c compartment] [-p] [-4] [-6] target_name 5 BY VIRGINEX

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ICMP/PING, Traceroute Options: -t -a -n count -l size -f -i TTL -v TOS -r count -s count -j host-list -k host-list -w timeout -R

-S srcaddr -c compartment -p -4 -6

Ping the specified host until stopped. To see statistics and continue - type Control-Break; to stop - type Control-C. Resolve addresses to hostnames. Number of echo requests to send. Send buffer size. Set Don't Fragment flag in packet (IPv4-only). Time To Live. Type Of Service (IPv4-only. This setting has been deprecated and has no effect on the type of service field in the IP Header). Record route for count hops (IPv4-only). Timestamp for count hops (IPv4-only). Loose source route along host-list (IPv4-only). Strict source route along host-list (IPv4-only). Timeout in milliseconds to wait for each reply. Use routing header to test reverse route also (IPv6-only). Per RFC 5095 the use of this routing header has been deprecated. Some systems may drop echo requests if this header is used. Source address to use. Routing compartment identifier. Ping a Hyper-V Network Virtualization provider address. Force using IPv4. Force using IPv6.

Optional Tracert Commands C:\Users\VIRGINEX>tracert Usage: tracert [-d] [-h maximum_hops] [-j host-list] [-w timeout] [-R] [-S srcaddr] [-4] [-6] target_name Options: -d Do not resolve addresses to hostnames. -h maximum_hops Maximum number of hops to search for target. -j host-list Loose source route along host-list (IPv4-only). -w timeout Wait timeout milliseconds for each reply. -R Trace round-trip path (IPv6-only). -S srcaddr Source address to use (IPv6-only). -4 Force using IPv4. -6 Force using IPv6. That’s all about ICMP, PING, and Traceroute. Hope it’s been informative for you! For more information keep visiting: http://vx-ccna-fm.blogspot.com.

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