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Webcast-Catalyst9k
New Member

Unable to ping routers interface IP

Initially we have 3 locations connected via metropolitan fiber links, say site A, B & C.

A,B,C are connected using 3550 L3 switches (IOS 12.1(22) EA1) on a separate VLAN.

Recently we have added 2 more sites, say, site D & E.

D is connected using 3640 router (IOS 12.2(24a).

E is connected using 2801 router (IOS 12.4(1c).

All runs EIGRP protocol with redistribute static.

I need help to troubleshoot an issue I am having.

A and B can ping D & E routers interface vice versa.

But C can't ping D & E routers interface vice versa.

C can ping A & B and also can see D & E inside LAN.

Where should I start in troubleshooting or any lead to possible cause?

Thanks a lot in advance.

6 REPLIES
Hall of Fame Super Gold

Re: Unable to ping routers interface IP

Benny

Probably you should start to troubleshoot this by verifying whether C has routes to D & E, and whether D & E have routes back to C.

If you want us to assist in troubleshooting it would be helpful if you would provide more detail about the topology and the output of show ip route from each router would be a good starting place.

HTH

Rick

New Member

Re: Unable to ping routers interface IP

Hi Rick,

Thanks for your reply.

As the interfaces are all on the same subnet, it shows the route of directly connected.

The issue was C can't ping only to D & E interface IP (10.3.254.11 & 10.3.254.12) and vice versa.

A has the ip route to D & E, so on C, I need to add the route to D & E LAN through A.

On D & E, I point all zeroes route to its outside interface.

Fyi, I am attaching the topology diagram and show ip route from ABC (in 1 file) and DE (in 1 file).

Hall of Fame Super Gold

Re: Unable to ping routers interface IP

Benny

This is a fairly interesting problem. And I think that we do not yet have quite enough information to be sure what the problem is but I have an idea. I note in the show ip route that router C leans routes only from addresses .2, .3, and .4 and learns no routes from .11 (router E) or from .12 (router D). I also note that router D learns routes from .2, .3, .4, and .11 but not from router C. And router E similarly learns routes from .2, .3, .4, and .12 but not from router C.

So router C does not learn from either D or E and D and E do not learn from C. This leads me to suspect that there is some layer 2 issue in which they do not have connectivity with each other. I note that your drawing does show links between C and D and E, but I suspect that these links are not working.

It might be helpful if you would post the output of show cdp neighbor detail from routers C, D, and E. I suspect that it will show that they are not seeing each other at layer 2. I also suspect that the output of show ip eigrp neighbor will show that C, D, and E are not forming neighbor relationships which would be consistent with a lack of layer 2 connectivity.

HTH

Rick

New Member

Re: Unable to ping routers interface IP

Hi Rick,

Routers D & E see only each other as neighbor.

Router C (as well A & B though)doesn't see D & E as neighbors.

I see all are listed in sh ip eigrp nei, but between C to D & E, there was retries and error Waiting for Init and Waiting for Init Ack.

I am attaching both sh cdp nei det and sh ip eigrp nei from C,D,E.

Thanks a lot for your assistance in resolving this strange problem.

Hall of Fame Super Gold

Re: Unable to ping routers interface IP

Benny

I believe that the output of show cdp neighbor detail is consistent with my theory that there is some layer 1 or layer 2 issue. I am quite surprised that the show ip eigrp neighbor shows as many neighbors on routers D and E.

I note that routers D and E have EIGRP on Ethernet and FastEthernet interfaces and C is on VLAN 254. Perhaps you could post configuration details of the interfaces/ports of each of these?

HTH

Rick

New Member

Re: Unable to ping routers interface IP

Hi Rick,

Thanks again for your continuous effort to resolve this puzzle.

I am attaching the requested info.

I would like to add more info as well.

On A,B,C sites, the MAN provider has their own switches connecting to our A,B,C interfaces on Vlan254, so the interface was put on switchport access vlan 254 and its IPs were configured on Vlan254.

On D,E sites, they only provide a fiber media converter to connect to the D,E routers interfaces, so the IPs were configured directly on the interfaces.

The provider has assisted by assigned the same 10.3.254.x IPs to the media converter and I can ping them from C as well as from D,E.

But C can't ping D,E interfaces IPs.

Why was the issue only on C?

A,B were configured the same way.

Thanks again.

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