One echo reply then TTL expired thereafter

[Fergal Meehan]

Hi,

I have a funny scenario that I can't get my head around on a customer network. I ping from LAN [10.10.10.0/23] to LAN [192.168.1.0/24] whom both run off the same switch. But I get one echo reply and then TTL expired. I clear the ARP and same result each time.

There are two 6509's. One per location.

There is a layer 2 and a layer 3 connection between both sites. The layer 3 is using both EIGRP & BGP but for now I'm not too concerned with layer 3 as the cause here.

It appears the switch at SITEB is ARP of the network so the question is why?

CONFIG @ SITEA

!

interface Vlan20

ip address 192.168.1.250 255.255.255.0 secondary

ip address 10.10.11.250 255.255.254.0

no ip redirects

!

So i guess the reason for the discontiguous networks on site A is that they ran out of addresses.

CONFIG @ SITEB

!

interface Vlan20

ip address 10.10.11.252 255.255.254.0

ip nat outside

!

Here's the thing, the above problem is resolved when the following was added @ siteB ip address 192.168.1.252 255.255.255.0 secondary is added to SVI 20 on site A!!

Can anyone shed some light on this and explain it to me? Why is site B trying to ARP for nodes on site A?

Thanks

F

[Panos Bouras]

Can you post the routing table, as I believe this is a L3 EIGRP / BGP case, multiple paths
Also can you tell me about the Nat settings?

Also please use either different VLANs on the 2 site eg VLAN 10 with ip 192.168.1.x and vlan 20 with ip 10.10.10.1.
Remember that the correct way is that each vlan must be on a different subnet for routing to work.


Sent from Cisco Technical Support Android App

[Fergal Meehan]

Apologies for slow reply. Unfortunately I have no access to the routing table to pull that information. I was working thru a 3rd party whom contacted me for advice.

The issue is resolved but I still suspect something wtrange with layer2.