Cisco 4000/2501 Routers able to ping in only one direction

Unanswered Question
Apr 1st, 2008

Hello:

I have two locations using Cisco Routers connected to Adtran ISU's connected via ISDN.

At Location A (MAIN SERVER SCO UNIX 5.0.6), I have a Cisco 4000 Router (connected to Adtran ISU's), and at Location 2 (REMOTE) I have a Cisco 2501 Router (also connected to Adtran ISU's.

Here is my problem...

When I am at the remote location - I can ping any IP device at that location (router, Micro Annex XL), AND I can ping Accross the ISDN line to the MAIN SERVER LOCATION, and ping any ip addressed equipment on that side ( Servers, Computers, printers, etc). But from the MAIN SERVER LOCATION, I can only ping the Router at the REMOTE location. Any equipment "behind" the router, at the remote site (Laptop, Micro Annex XL) cannot be "ping"ed from the Main Location.

Since this is the case I cannot get my server - at the MAIN LOCATION to COMMUNICATE with WYSE 60 dumb terminals at the REMOTE SITE through the Micro Annex.

By the way I can also VPN (using my Laptop) from the Remote site to a CITRIX METAFRAME SERVER at the MAIN LOCATION - but oddly enough even the CITRIX server cannot "ping" the laptop across the routers?

Is there a Cisco Setting in either of the Cisco Routers that could be responsible or is there something else going on here? Ny suggestions would be appreciated?

Regards

Arif

I have this problem too.
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Richard Burts Tue, 04/01/2008 - 12:08

Arif

There are several things that might be responsible for this. It is possible that there is an access list on one of the router interfaces that is blocking traffic. My guess based on the information so far is that there may be some issue with routing information on one side or the other. Could you post the output of show ip interface brief and of show ip route from both the 4000 router and the 2501 router? This may help us to find the problem.

HTH

Rick

a.dhalla Tue, 04/01/2008 - 17:06

Hi Rick Thanks for your help. Here are the router outputs that you requested. Please let me know your thoughts.

1. show ip interface brief 2501 router (remote)

home#show ip interface brief

Interface IP-Address OK? Method Status Protocol

Ethernet0 128.1.9.254 YES NVRAM up up

Serial0 128.1.8.2 YES NVRAM up up

Serial1 unassigned YES not set administratively down down

2. show ip interface brief 4000 router (main)

calrouter#show ip interface brief

Interface IP-Address OK? Method Status Protocol

Serial0 128.1.254.1 YES NVRAM up up

Serial1 128.1.8.1 YES NVRAM administratively down down

Serial2 128.1.6.1 YES NVRAM up up

Serial3 128.1.8.1 YES NVRAM up up

Serial4 unassigned YES not set administratively down down

Serial5 unassigned YES not set administratively down down

Ethernet0 128.1.1.254 YES NVRAM up up

Async1 unassigned YES not set down down

Dialer8 unassigned YES not set up up

3. show ip route 2501 (remote)

home#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default

Gateway of last resort is not set

128.1.0.0 is variably subnetted, 8 subnets, 2 masks

R 128.1.254.0 255.255.255.0 [120/1] via 128.1.8.1, 00:00:00, Serial0

R 128.1.1.0 255.255.255.0 [120/1] via 128.1.8.1, 00:00:01, Serial0

R 128.1.2.0 255.255.255.0 [120/2] via 128.1.8.1, 00:00:01, Serial0

R 128.1.7.0 255.255.255.0 [120/2] via 128.1.8.1, 00:00:01, Serial0

R 128.1.6.0 255.255.255.0 [120/1] via 128.1.8.1, 00:00:01, Serial0

C 128.1.9.0 255.255.255.0 is directly connected, Ethernet0

C 128.1.8.1 255.255.255.255 is directly connected, Serial0

C 128.1.8.0 255.255.255.0 is directly connected, Serial0

4. show ip route 4000 (main)

calrouter#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default

Gateway of last resort is not set

128.1.0.0 is subnetted (mask is 255.255.255.0), 7 subnets

C 128.1.254.0 is directly connected, Serial0

C 128.1.1.0 is directly connected, Ethernet0

R 128.1.2.0 [120/1] via 128.1.254.2, 00:00:03, Serial0

R 128.1.7.0 [120/1] via 128.1.254.3, 00:00:17, Serial0

C 128.1.6.0 is directly connected, Serial2

R 128.1.9.0 [120/1] via 128.1.8.2, 00:00:09, Serial3

C 128.1.8.0 is directly connected, Serial3

Thanks

Arif

Richard Burts Wed, 04/02/2008 - 10:48

Arif

When I read the symptoms I expected to find some mismatched address or some entry missing from one of the routing tables. But the additional output that you have posted does not show this. So we must look for something else.

First I would like to ask for some clarification. When you are doing the pinging (at both sites) where are you pinging from? Is it from the router, is it from a device behind the router? I would also like to ask whether you have the problem with every device behind the router at the remote site?

I would also like to ask if there is a possibility that there are firewalls running on devices at the remote that prevent responding to ping?

I am considering the possibility that there might be an access list or something like that which is impacting traffic. Can you post the config of both routers?

HTH

Rick

a.dhalla Wed, 04/02/2008 - 12:17

Rick,

Some other information you may need. This setup has been running for almost 5 years no problem. About 3 weeks ago, the line connection dropped and we troubleshooted everything we could to find out what could have been the problem. Long and the short, could not find anything so we left it alone for a few days. During that time, the link came back up on it's own. The reason I mention this is so you know that original configs in both routers were set up to work and did work. The problem I posted is my current problem which makes no sense to me.

Server Side has setup as follows :

Server --> switch -- > router -- > adtrans -- > ISDN line

Remote side has setup as follows

Dumb terminals -- > Annexe -- > Hub -- > Router -- > Adtrans -- > ISDN

When I am at the server site, I ping from the Unix server OR from a PC connected on the LAN at server side. Both times, I can ping the router at the REMOTE site but nothing past it.

When I am at the REMOTE site, I plug a notebook into the hub and I can locally ping the router and the Annexe box. Also, I can ping across the router to ANY DEVICE with an IP at the main server site. Also, I can telnet through the router to the server side and log on to the UNIX server. Also, can do the same thing with a citrix server.

There are no firewalls at the REMOTE site, but my notebook does have a firewall which I did not disable. To confirm if this is why the ping request came back unreachable, I will re-do with notebook turned off.

On the server side, we do have a hardware firewall. No setting changes to this from the time frame of system working to right now, when it does not work.

Attached file shows config of both routers.

Thanks.

Arif

Richard Burts Wed, 04/02/2008 - 13:45

Arif

Thanks for the additional information. I have looked at the configs and I notice one thing: on the 4000 router under interface serial3 I would expect to find the command dialer-group 8. But it is not there. I am not clear whether it is present in the real running config and somehow got dropped in the version that you posted or whether it really is missing.

If the dialer-group is missing it would have a couple of impacts: the router could answer a call but not place a call, calls that it does answer would disconnect at the expriation of the dialer idle timeout which defaults to 2 minutes. The dialer-group and associated dialer-list (which is present in the config) are what recognize interesting traffic and reset the idle timer).

If the dialer-group 8 is missing I suggest that you put it into the config and see if it makes a difference in the behavior.

HTH

Rick

a.dhalla Thu, 04/03/2008 - 14:08

Rick,

Have added the dialer-group 8 into the serial interface 3 and then saved to memory.

Have cycled up and down and no change... still can not ping the annexe after the router at REMOTE site. REMOTE site can not connect via Wyse 60's to server side.

Any other thoughts ?

Alykhan

Richard Burts Thu, 04/03/2008 - 19:45

Alykhan (or is it Arif?)

I had hoped that it would be the dialer-group was the issue. If not we will look for something else. I went back to an earlier post and see this:

When I am at the server site, I ping from the Unix server OR from a PC connected on the LAN at server side. Both times, I can ping the router at the REMOTE site but nothing past it.

I would like some clarification about which address you ping on the remote site router, if it the ISDN interface address or the LAN address?

HTH

Rick

a.dhalla Fri, 04/04/2008 - 06:40

Rick,

For names it is both of us. Arif and ALykhan both are working on this problem to try and solve.

The Adtran ISDN interface does not have an IP so we are pinging the cisco router on the other side. Since we can get to the router, we assume that the interfaces at both ends are working and that the cisco 4000 at server site also works. Also, since we can ping from the REMOTE site (from a notebook plugged into the hub) and we can also telnet to the servers from the notebook, we assume that the cisco 2501 router at the REMOTE site must be working fine.

Things that don't make sense to us are as follows :

At REMOTE site locally we can ping the Annexe when connected to that hub, BUT WE CAN NOT ping the Annexe from the Server Site.

Alykhan

Richard Burts Fri, 04/04/2008 - 09:37

Alykhan

Perhaps my question was not clear: the remote router has 2 IP addresses (128.1.8.2 (or in the posted config 192.1.8.2) and 128.1.9.254 (or in the posted config 192.1.9.254)). Which address are you pinging when you ping from the server?

Another thought has occurred to me: can you please tell us what IP address, what subnet mask, and what default gateway are configured on the Annexe?

HTH

Rick

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