Subject: Re: [vserver] transient network drops
From: Eugen Leitl <eugen@leitl.org>
Date: Sat, 1 Sep 2007 11:30:39 +0200

On Sat, Sep 01, 2007 at 02:31:47AM +0200, Herbert Poetzl wrote:

> well, most likely, spanning tree is the magic word here :)
> 
> (http://en.wikipedia.org/wiki/Spanning_tree_protocol)

I use spanning tree since my firewalls are redundant (STP
disables one firewall, which gives you a poor man's
failover capacity -- sure no carp+pfsync). 

However, in this case the outages are intermittant, and what
happens is every couple hours or so the switch suddenly notices
a packet with a MAC which used to be on port 6 suddenly comes
in at port 49, at which point it ignores anything with that
MAC on port 6 until the period of MAC aging expires, and it
decides it's been port 6 after all.

So why would

	switch-1 (level 3)
	 |     |
	NIC1   |
	system |
	NIC2   |
	 |     |
	switch-2 (level 2)

do that? Notice that the system doesn't route. It all
happens at Ethernet frame level.

-- 
Eugen* Leitl <a href="leitlhttp://leitl.org">leitl</a> http://leitl.org
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