Strange issue with ping

Answered Question
May 10th, 2007

Hi Friends ... Manoj here ..Need you help to resolve the issue.

I have a router in Japan and am trying to ping a server that is located in US. I have an MPLS link to ISP. When I do a ping to the server, it times out. However, when i do an extended ping with the source as either the LAN or loopback interface and destination as the server, the ping is successfull. I have verified with ISP and they confirmed there is no issue from their end.

Cheers!!!

I have this problem too.
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Correct Answer by patrickvanham about 9 years 7 months ago

The outgoing interface is probably not routable from the destination. When you sepcify loopback or LAN interface the destination is able to return the traffic.

Some MPLS configurations do not assign an IP address to the physical interface and only use loopbacks for connectivity. That may be the case with you. Which interface is outgoing to the ISP and what IP address, if any, is assigned to it? If one is assigned, does the router in the US have a valid return path?

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Correct Answer
patrickvanham Thu, 05/10/2007 - 09:34

The outgoing interface is probably not routable from the destination. When you sepcify loopback or LAN interface the destination is able to return the traffic.

Some MPLS configurations do not assign an IP address to the physical interface and only use loopbacks for connectivity. That may be the case with you. Which interface is outgoing to the ISP and what IP address, if any, is assigned to it? If one is assigned, does the router in the US have a valid return path?

ankbhasi Thu, 05/10/2007 - 09:36

Hi Manoj,

When you initiate a normal ping bydefault it takes the source ip of your exit interface. I believe your remote end router does not have a route back to your wan interface of Japan router.

Can you access your remote end router and do "sh ip route " and see if the route is available.

Also check for any ACLs on Japan as well as remote end router.

Regards,

Ankur

Manoj Wadhwa Thu, 05/10/2007 - 10:15

Hi Ankus,

As i dont have access to US routers, i just checked with the US team and they confirmed that they do not accept our MPLS interface ip, hence direct ping is not working. Thanks for your assitance. Appreciate very much.

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