Seconday IP Address Issue on ISR 4431 Router

[taufeeq taufeeq]

Dears,

The secondary IP address on routers physical interface is not working. Your help will be much appreciated.

IOS is: Cisco IOS XE Software, Version 03.13.02.S - Extended Support Release.

The config is as follows

interface GigabitEthernet0/0/1
description xxxxx
ip address 185.110.x.x 255.255.255.x secondary
ip address 87.101.x.x 255.255.255.x
load-interval 30
speed 1000

Currently the primary IP which is 87.101.217.x 255.255.255.x is working very well. 

Thanks in Advance,

Regards,

Taufeeq.

[Mark Malone]

Hi

can you elaborate on what you mean exactly by its not working ?

Also the image your on is an ED early deployment and looks like 1 step away from being deferred , the recommended image for that platform in your train is 3.13.4S its an MD release and safe harbour just in case you have hit a bug

[taufeeq taufeeq]

Hi Mark,

We have a subnet using the secondary IP to reach internet. When I assign the same IP to physical interface as primary its working very well. The moment I configure it as secondary IP it doesnt work. Primary IP on the same interface does work.

[Richard Burts]

Taufeeq

It is very odd that it works when the subnet is configured as the primary address but fails when it is configured as secondary address. There are several possibilities that occur to me which might cause this symptom. The first one that I would like to explore is the possibility that ARP is not working correctly with the secondary subnet. Would you configure the address as secondary, run debug arp (or perhaps debug ip arp depending on your platform), and post the debug output.

HTH

Rick

[taufeeq taufeeq]

Hi Richard,

Thank you for your response.

without doing any config changes it just started working fine. 

Regards,

Taufeeq

[Richard Burts]

Taufeeq

It is surprising that it did not work, and then without any config change that it did start to work. Perhaps it was due to something like an incorrect ARP entry and then that entry aged out and was replaced by a correct entry.

Thank you for posting back to the forum and letting us know that it is working now.

HTH

Rick

[taufeeq taufeeq]

Thank you Mark. Its working.