Re: VRRP packets with duplicate AH sequence number

On 2017-05-18 11:31, Graeme Fowler wrote:
> On 17 May 2017, at 21:56, Quentin Armitage <[email protected]> 
> wrote:
>> This appears to confirm that keepalived is only sending the packet 
>> once, but for some reason the packet is being looped back to the 
>> keepalived process multiple times (in this case 86 times)
> 
> Aleksey, are you by any chance running an LVS director and services on
> these two boxes?
> 
> This looks to me like the old, old problem of running a director and
> realserver on the same host, which can result in packets being
> ‘reflected’ if they get processed by the LVS rules that are in place.
> 
> It probably/possibly isn’t, but it looks familiar.
> 
> Graeme

Graeme,

nothing except fresh system and keepalived on new machine.

Quentin,

Well, seems you are right and the packets get looped somewhere in the 
network. I'll try to find out where and why. The most confusing thing is 
that when keepalived receives the packet with duplicate seq number, it 
increases it's own counter - so there is a huge gap between the last 
non-duplicate packet (let's assume it has seq num 10 for example) and 
the first packet after duplicates stop arriving (let's call it seq num 
100). So the packets with seq num 11-99 are not sent on the network.

I'll get in touch when I figure out what causes these loops - my network 
is loop free (at logical level using STP) - however, probably there are 
some bugs in switch firmware which allows multicasts to penetrate 
through STP block. However it does not explain why only single packet is 
being duplicated multiple times and what triggers such a behavior.

Thanks a lot for your help and your time.

-- 
With kind regards,
Aleksey

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