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Re: Bug? ARP with wrong src IP address

To: Carlos Velasco <carlosev@xxxxxxxxxxxx>
Subject: Re: Bug? ARP with wrong src IP address
From: Julian Anastasov <ja@xxxxxx>
Date: Thu, 24 Jul 2003 18:54:04 +0300 (EEST)
Cc: Bart De Schuymer <bdschuym@xxxxxxxxxx>, <netdev@xxxxxxxxxxx>
In-reply-to: <200307241728270476.0031BAB0@xxxxxxxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
        Hello,

On Thu, 24 Jul 2003, Carlos Velasco wrote:

> The problem is more complicated than the simplified setting I have builded 
> for describing the bug:
> Real setting and meaning of the lo interface is because I'm using IOS Load 
> Balancing in dispatched mode on Cisco Catalyst 6500.
> This cause packets being sent to a server farm of Linux boxes with 
> destination IP the one configured on the loopback interface in all machines.
> In the ethernet interface all Linux boxes have diferent IP address and the 
> balancing device send the packets through any of these interfaces, choosing 
> the "leastconnections" server.
> Thus, the load balancing device only change the mac address of the real 
> packet on the fly sending it to one of the real servers where it's accepted 
> cause of destination IP is the loopback IP address on every Linux machine.
>
> Problem is when the packet go back to the balancing device, as they send ARP 
> request with loopback source IP address, that cause Cisco device not to reply 
> the ARP request.
> I have tried different IOS and Cisco devices, no one reply this ARP request.

        I now see, it is the so called "ARP Problem" in the IPVS
context, many real servers and one director sharing same virtual
IP:

http://www.linuxvirtualserver.org/

The most used feature for such setups:
http://www.ssi.bg/~ja/#hidden

> Regards,
> Carlos Velasco

Regards

--
Julian Anastasov <ja@xxxxxx>


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