Re: [Keepalived-devel] VMAC, vmac_xmit_base, and IGMP

[Patrick S. <ne...@bo...>]

Hello Alexandre,

On Monday 23 June 2014 13:52:47 Alexandre Cassen wrote:
> 
> Well, some switch are updating their CAM according to IGMP join msg (cisco
> are doing it), so if you are using switch like that vmac_xmit_base must be
> used.

Isn't that just the normal switch source MAC learning in action there? i.e. it 
will happen on just about any switch in existence?

Is there an exception in the ethernet standards that disables (should disable) 
source MAC learning for IGMP multicast (or general multicast)?

best regards
  Patrick

> On 27 May 2014, at 17:44, Patrick Schaaf <ne...@bo...> wrote:
> > Hi,
> > 
> > "playing" with the VMAC feature on a keepalived 1.2.13 driven cluster of
> > balancers, I noticed a peculiar "feature" that I saw no mention of in the
> > documentation. Thought I'd note it here...
> > 
> > I am running a ping to the VRRP address from an internal host. Then I
> > restart one of the BACKUP keepaliveds. And notice a single ping to
> > receive an "ICMP host unreachable" reply with source the IP address of
> > that BACKUP balancer.
> > 
> > Looking into it with tcpdump, I notice that when the daemon starts, it
> > sends IGMP messages with source MAC the VMAC - thus teaching the switch,
> > for a short while, that it would like to have packets for the VMAC.
> > 
> > Adding vmac_xmit_base to the configuration fixes the issue - the IGMP
> > messages are then sent with the base interface source MAC address.
> > 
> > In practise the "error interval" will probably be smaller, due to the
> > MASTER balancer more continuously sending packets with VMAC source - my
> > test setup has no operational traffic or I probably wouldn't have
> > noticed.
> > 
> > I don't know whether this could be considered a bug, or at what priority,
> > or what to do about it, except maybe adding another reason in the docs
> > why vmac_xmit_base might be a good idea.
> > 
> > I'll close with a curious question: are there reasons why vmac_xmit_base
> > is
> > NOT a good idea?
> > 
> > best regards
> > 
> >  Patrick
> > 
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