[c-nsp] HSRP issues on Cisco3550

[Gert Doering]

Hi,

On Wed, Nov 08, 2006 at 03:52:12PM +0000, Sam Stickland wrote:
> I'm not sure I understand this - wouldn't the standby router populate 
> it's CAM table from the ARP replies? And it has to send out and ARP 
> reply (and get a response), or the router can't populate the destination 
> MAC address in frame.

The problem is that the standby router will have an ARP timeout of 4 hours
(default) while the switches in between will have a CAM timeout of 
much less (default is 300 seconds, if I remember correctly).

When the CAM tables timeout, the ARP tables are still valid for nearly
4 hours - and in that time, the switches will not see packets from 
the end hosts (no ARP, and all normal packets go to the other router)
so you'll end up with flooding.

(Ethernet just sucks).

gert
-- 
USENET is *not* the non-clickable part of WWW!
                                                           //www.muc.de/~gert/
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de