Re: Router stops routing after changing MAC Address

[Michael Clark <michael@metaparadigm.com>]

Stephen Hemminger wrote:

>On Fri, 10 Mar 2006 18:33:15 -0600
>"Greg Scott" <GregScott@InfraSupportEtc.com> wrote:
>
>  
>
>>Hello - This feels like a kernel issue.  I spent hours and hours and
>>hours looking for documentation and archives around this but did not
>>find anything.  
>>
>>I have a Linux router and I need the ability to swap hardware without
>>causing downtime.  The problem, of course, is ARPs.  The NICs in the
>>replacement system need the same MAC Addresses as the NICs in the
>>original system.  I'd like this all to be in the kernel and not depend
>>on a daemon process that can die.
>>
>>How to change MAC addresses is documented well enough - and it works -
>>but when I change MAC addresses, my router stops routing.  From the
>>router, I can see the systems on both sides - but the router just
>>refuses to forward packets.  Here are my little test scripts to change
>>MAC Addresses.
>>    
>>
>
>You probably just need to flush the route cache after the address change?
>  
>
Or do a gratutious arp for the address with the new HW address (tool to
do this is included in HA failover software such as heartbeat and others).

~mc