From: James Ventre (messageboard@ventrefamily.com)
Date: Fri Dec 09 2005 - 09:33:12 GMT-3
Unicast flooding is a problem when your router and cam timers aren't in
sync. The router spits the packets out (to the MAC it got from it's ARP
entry) and send it down to the switch. The switch doesn't have that MAC
address in it's cam table (cause the device hasn't spoken in a long
time) so it floods it out all of the ports in the VLAN (except for the
one it received it on). Once the device talks and it can dynamically
learn the mac - unicast flooding stops.
In my designs, I usually make the router interface arp timer 300 seconds
(to match the switch), but you can raise the cam timer if you want ....
just so long as they match. This way, when the router needs the arp
entry .... it'll broadcast an arp packet ... the host will reply and the
switch can learn the mac as the router learns the arp information (being
in sync is the goal)
James
Schulz, Dave wrote:
> Brian -
>
> Can you explain this a little. I looks like in the example that you cite, the
> MAC address is picked up at the port dynamically. Wouldn't this be the
> default behavior?
>
> Dave
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