E1 circuit loop testing

Answered Question
Jan 20th, 2009

Im having a circuit connecting RouterA to Router B. This circuit is problematic thus the provider gave a hard loop somewhere near to Router B facing towards Router A.

I am able to see the loop in Router A.

My question is, when I ping my own interface ip in Router A Serial interface, would the ICMP packet goes through the providers line till where the loop was given and comeback? Would the icmp packet leave the router even when pinging its own interface ip address?

I have this problem too.
0 votes
Correct Answer by Richard Burts about 7 years 10 months ago

Sadrudin

Yes. The ICMP packet will leave the interface, travel over the link till it gets to the loop, and will then return to you.

It is one of the basic behaviors of Cisco IOS that when you ping your own interface address on a point to point serial link, that the router actually sends the ICMP out on the link. The ICMP should arrive at the other end of the point to point serial and be forwarded back. (the ping response also travels over the point to point serial link). It is an interesting test and I suggest that you ping the neighbor on the point to point serial link and then ping your own interface address. The response times for ping to your own address should be double the response time to ping the neighbor.

HTH

Rick

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Correct Answer
Richard Burts Tue, 01/20/2009 - 03:57

Sadrudin

Yes. The ICMP packet will leave the interface, travel over the link till it gets to the loop, and will then return to you.

It is one of the basic behaviors of Cisco IOS that when you ping your own interface address on a point to point serial link, that the router actually sends the ICMP out on the link. The ICMP should arrive at the other end of the point to point serial and be forwarded back. (the ping response also travels over the point to point serial link). It is an interesting test and I suggest that you ping the neighbor on the point to point serial link and then ping your own interface address. The response times for ping to your own address should be double the response time to ping the neighbor.

HTH

Rick

Richard Burts Tue, 01/20/2009 - 04:13

Sadrudin

I am glad that my response resolved your question. Thank you for using the rating system to indicate that your question was resolved (and thanks for the rating). It makes the forum more useful when people can read a question and can know that a response did resolve the question.

The forum is an excellent place to learn about Cisco networking. I encourage you to continue your participation in the forum.

HTH

Rick

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