Re: lvs-dr

To: Jared Cook <jared.cook@xxxxxxxx>
Subject: Re: lvs-dr
Cc: <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
From: Julian Anastasov <ja@xxxxxx>
Date: Tue, 29 May 2001 22:51:51 +0000 (GMT)

On Tue, 29 May 2001, Jared Cook wrote:

> I am having a problem with lvs-dr.  I have set up a telnet test lvs-dr and it
> works fine for a while.  After some time though, it only forwards traffic to
> one of the two real servers.  I don't think I have "the arp problem" becasue
> I have the virtual IP on seperate nics on a differnet physical network
> (crossover cable between the two realservers.  Going to be an OPS cluster.)

        You can have ARP problem with DR setup if:

1. one real server can see the broadcasted ARP probes for VIP sent from
the incoming router/local LAN client

2. one real server uses the incoming router/the LAN client as uplink
router/next hop (incoming router here is the uplink router that feeds
the director with requests after resolving the VIP using ARP).

        I assume your problem is in (2)

> I have found that I can correct this problem by issuing the 'arp'  command on
> the director.  What can I do to avoid having to give the arp command every 15
> minutes?

        Topology, please, links. It seems this is an ARP issue. If you
still don't think this is an ARP problem, you can prove it with
"tcpdump -len arp" outputs after deleting the ARP entries (arp -d VIP)
and flushing the routes (linux: ip route flush cache).


Julian Anastasov <ja@xxxxxx>

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