![]() ![]() These tools are usually run at a Microsoft Windows Command Prompt. ICMPs are used by routers, intermediary devices, or hosts to communicate updates or error information to other routers, intermediary devices, or hosts. Internet Control Message Protocol (ICMP) is an error reporting and diagnostic utility. Traceroute, Ping, MTR, and PathPing are network tools or utilities that use the ICMP protocol to perform testing to diagnose issues on a network. In my experience this how Cisco and Juniper routers behave, I'm not sure about other vendors.Using Traceroute, Ping, MTR, and PathPing So while the actual ICMP traffic generated by R1 is going back to R5 via R3, the IP header of ICMP Unreachable message will have the source of ingress interface 10.1.12.1. VRF info: (vrf in name/id, vrf out name/id) Loose, Strict, Record, Timestamp, Verbose: The traceroute output from R5 looks as following: R5#traceroute Route metric is 0, traffic share count is 1 As you can see, the forward path is via R4-R2, while reverse path is R3-R4. Let's assume we are souring the traceroute from R5's loopback 5.5.5.5 to R1's loopback 1.1.1.1. This usually make the traceroute much easier to read.Īs a follow-up to YLearn's question I'm posting a network diagram and some outputs. In reality, it is very likely that you will face non-standard behavior where router will source the ICMP reply with the source of ingress interface. ![]() Ping -R 10.2.105.178 PING 10.2.105.178 (10.2.105.178) 56(124) bytes ofĦ4 bytes from 10.2.105.178: icmp_req=5 ttl=253 time=74.1 ms NOP RR:Ħ4 bytes from 10.2.105.178: icmp_req=6 ttl=253 time=13.0 ms NOP RR:ġ0.2.105.218 #change every time, Idon't know why#Īccording to RFC1812 the source address of ICMP message generated by the router should be that of the egress interface over which the packet would normally return to the sender. That's an real example on my internet provider net, maybe not so clear, but I don't have just now some router to link each other :) traceroute 10.2.105.178 Only in this case, the returning path is the IP address of the outgoing interface you are asking for. So you can see also the return path of the ECHO_REQUEST, that is not the exit interface (that you are asking about) unless the outgoing path is the same of the come back path. Many hosts ignore or discard this option. Note that the IP header is only large enough for nine such routes. Includes the RECORD_ROUTE option in the ECHO_REQUEST packet and displays the route buffer on returned packets. I'm coping-post the option -R of ping man page: I's not exactly the answer at your question, but that a simple (but limited) way to do (in certain case) what you want. Rtt min/avg/max/mdev = 47.441/47.441/47.441/0.000 msĪnd this is the IP address of my dial-up connection.īut it has not been recorded by the ping command. This is the traceroute to a public web server: I tried the ping -R suggestion but it does not seem to work. Every node in between has an incoming and an outgoing interface.Įxecuting traceroute -n dst on src will show the IP addresses of src, dst and all incoming interfaces of the hops in between.īut how to trace the outging IP addresses? The Unix command traceroute traces the IP addresses of the nodes from a source node to a destination node. ![]()
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