Re: VRRP and the kernel

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: VRRP and the kernel
From: Alexandre Cassen <Alexandre.Cassen@xxxxxxxxxx>
Date: Fri, 23 Nov 2001 21:55:49 +0100

> >I see big problems for setups where the VRRP routers have
> >two or more devices attached to same hub. When the normal hosts
> >try to resolve the VIP via ARP they will receive many ARP replies
> >from the current MASTER.
> => Yes the same MASTER.

        After reading your next words it seems the hosts will
receive only one ARP reply, from the device where the MASTER is bound.

Yes we are sync :)

> >The question is: are these replies equal, i.e. containing same src MAC?
> Yes : A MASTER mean a VRRP Instance in MASTER state, which mean VRRP VIPs
> owned on the LVS director where VRRP Instance are in MASTER state. We know
> that VRRP Instance state are uniq and identified by a uniq VRID on the
> whole VRRP topology.

        IMO, there is also another question: why we restrict packets
to VIP to come only through once device (switch port)? Of course,
this is not true for all network stacks but Linux can do it: one
subnet reachable through many devices (at least the packets can
be received through many devices) but there is a way to send through
many devices. Anyways.


> >    But then the required behavior is to reply with 3 different
> >MACs if we have 3 NICs?
> => hmmm, is to reply with VMAC associated with a specific VIP. A specific
> VIP belong to the VRID in MASTER state owning this VIP. And only on VRID is
> active at a time. Agreed ?

        May be I don't fully understand the VRRP terms and internals
but as your hands are durty with VRRP


, do you see any variant to
allow we to reply for one VIP through many devices with different
VMAC (of course, the VRRP protocol may be will use only one device
but for me, this is also questionable).

I agree with you... but it can be a starting point ?

> Physical topology is :
>              WAN SIDE
>                 |
>     +-----------------------+
>     |      SWITCH/HUB       |
>     +-----------------------+
>       |                   |
>       | eth0              | eth0
>      +-----+           +-----+
>      | LD1 |           | LD2 |
>      +-----+           +-----+
>       | eth1              | eth1
>     +-----------------------+
>     |      SWITCH/HUB       |
>     +-----------------------+
>                  |
>                LAN SIDE

        This explains everything :))) Only one ARP reply per request.

Yes I think this is a very very simple/common setup, it can be a good starting point.

But you are more advanced than I in MAC handling inside kernel so no matter for me if you say that it is too restrictive.

Best regards,

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