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

[Alexandre C. <ac...@gm...>]

Hi Patrick,

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.

regs,
Alexandre

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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