Re: Re: why can VS-DR work?

To: nsr1@xxxxxxx
Subject: Re: Re: why can VS-DR work?
Cc: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
From: Joseph Mack <mack@xxxxxxxxxxx>
Date: Fri, 29 Oct 1999 18:24:34 -0400 (EDT)
On 29 Oct 1999 nsr1@xxxxxxx wrote:

> What happens if arp is turned on?

> > client's IP = CIP
> > director's IP = DIP
> > realserver's IP = RIP
> > virtual IP = VIP

a packet arrives at the gateway/router for the LVS with source=CIP,
dest=VIP. The router puts out an arp request "who has VIP? tell routerIP".
In the working case only the director replies and it receives the packet.
If the VIP on the realservers also replies to arp requests, then the
router will get multiple replies. You have multiple machines on a network
with the same IP. Quite what happens next I'm not sure, but the LVS
doesn;t get the packets in the right places and no replies go back to the
client. The network for the LVS can freeze or at least be very unhappy.


Joseph Mack mack@xxxxxxxxxxx

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