[CentOS] change network switch need 'arp" clear cache?

Les Mikesell lesmikesell at gmail.com
Tue Feb 23 19:58:30 UTC 2010


On 2/23/2010 1:25 PM, mcclnx mcc wrote:
> we plan to change network switch and firewall machine to new one.  Network engineer told me after switch and firewall equipment change I may need run 'arp ..." to clear out cache on every CENTOS servers due to switch and firewall MAC address change.
>
> we have 30 to 40 CENTOS 4.X and 5.X my affect.  my question are:
>
>
> 1. does switch and firewall equipment change need LINUX client clear cache?
>
> 2. if needed, how to clear cache and get new info about switch and firewall?

I'm not sure about the exact timing, but Linux is pretty aggressive 
about updating arp entries automatically.  I think entries time out in a 
minute or so of inactivity and are re-probed on delays anyway.  On the 
other hand, routers have much longer times for their arp cache, so it 
probably will be necessary to clear the router on the other side of the 
firewall.  Switches normally act transparently at layer 2 so connections 
through them (as opposed to management connections _to_ them) don't care 
about addresses.

-- 
   Les Mikesell
    lesmikesell at gmail.com


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