Routing weirdness

Ryan Leathers ryan.leathers at globalknowledge.com
Mon Apr 26 14:33:35 BST 2004


One word: portfast

Or is that really two words  ;)

On Fri, 2004-04-23 at 13:20, Peter Mueller wrote:
> > I've seen a similar delay in failover when using cisco routers.  They
> > don't update the internal MAC address table after receiving gratuitous
> > arp packets during an LVS director failover event.  I don't 
> > know if the
> > heartbeat package uses arps to fail over, but keepalived does.  Cisco
> > routers seem to need icmp packets before they'll update the 
> > MAC address
> > table.  For LVS, the problem here is that the router continues to send
> > traffic to the VIP at the master's hw address instead of 
> > shifting to the backup's hw address.
> 
> Heartbeat sends out quite a few gratuitous arps.  They are very good about
> it.  Only a misconfigured switch or an extremely crappy switch wouldn't
> respond to the arps that heartbeat sends out.  Another possibility here is a
> firewall or misconfigured linux is blocking the arps.
> 
> As Horms said, the best way to figure out what is going on is through the
> use of tcpdump from a few points of presence on your network.  Logging in to
> the switch to see what the arp entries are before and after failover is also
> not a bad idea.
> 
> P
> 
> ---
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-- 
Ryan Leathers <ryan.leathers at globalknowledge.com>
Global Knowledge



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