Question : Problem: Alcatel anybody?

I have an OMNISWITCH/ROUTER

Can anybody tell me how do I reduce the xlate timeout period?

I want my xlat table to flush all entries every 30 minutes.

Answer : Problem: Alcatel anybody?

I know of three ways that can give this kind of effect:

1.  La Brea
  This is a tool to slow down the spread of worms that scan a whole address range.  It will "populate" vacant addresses by responding to ARP requests that repeat (i.e., *apparently* were unanswered).  Anybody running such a tool on your network?  Only authorized admins who understand what they're doing should be.

2.  Ettercap, or similar "ARP poisoning" tools
  These allow a switched network to be sniffed, by corrupting the switch ARP tables to redirect traffic of interest to a monitoring port without requiring admin access to the switch.  Nobody should be authorized to do this on a production network and keep their job....

3.  Proxy ARP
  A router may be configured to believe that it is the gateway between the network where it saw an ARP request, and the network where the destination is located.  If these are the same network, something's misconfigured or misconnected.