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Had a thought on this - You could use iptables to mark your return packet, then
run it through a separate routing table based on a 'i ip ru add fwmark x table
y' option. Your separate routing table would just have a default gw pointing to
the VIP from your LVS cluster.
Not sure if that would work well, but it's worth a shot.
On Mar 1, 2012, at 8:59 AM, Dean Scothern wrote:
> Thank you for your quick reply.
>
> Whilst snat would work I would prefer not to use it as it hides the source ip
> of the packets, making applications that use ip access lists more problem
> atic to configure, eg mailservers. Eventually I would expand the clients to
> include other networks (internet), and would like log analysis to work.
> I would prefer not to use a proxy and pass magic headers with the remote ip
> them either.
> The link in question also probably cannot easily apply to redhat/centos 6 as
> they are based on 2.6.32 kernel and the link mentions 2.6.35, 2.6.36.
> Reading further it might be possible to apply the patch set and rebuild the
> associated kernel modules.
>
> To be honest I hoping for some route configuration magicry, I feel so close
> and surely there must be a way.
>
> Many Thanks
>
>
> From: David Coulson [mailto:david@xxxxxxxxxxxxxxxx]
> Sent: 01 March 2012 13:04
> To: LinuxVirtualServer.org users mailing list.
> Cc: Dean Scothern
> Subject: Re: [lvs-users] annoying routing problem with a lvs cluster
>
> You need to SNAT real server traffic going to your real servers.
>
> Quick google found this:
>
> http://blog.loadbalancer.org/enabling-snat-in-lvs-xt_ipvs-and-iptables/
>
> I'm presuming it's in mainline by now, but I know it's not in RHEL/SuSE yet.
>
> David
>
> On 3/1/12 7:55 AM, Dean Scothern wrote:
> Hi,
>
> I've been experimenting with a slightly non standard lvs cluster arrangement.
>
> I have a set of combined real servers/real clients (each machine has both
> services and clients) and two machines running lvs as a cluster.
>
> All machines are connected directly to the same two networks: frontend and
> backend.
>
> The real servers/real clients connect to a service ip on the lvs machines on
> the frontend network.
> The lvs machines run in masq mode and connect to the real servers/real
> clients on the backend network.
> I've configured policy routing on the real servers/real clients backend
> interfaces to return traffic via a second gateway on the lvs hosts.
>
> This works very well except when a real server/real client connects to its
> own backend interface via the lvs cluster ip.
> I guessing that the local host route means that instead of returning the
> traffic via the backend gateway on the lvs it tries to go directly locally.
> Tcpdump appears to support this guess and if I turn on martian logging I can
> see the traffic.
>
> Initially I thought that reverse path filtering was preventing operation but
> the problem remained when it was disabled.
> Turning on routing had not beneficial effect either.
>
> Ideally I would like to setup routing to override the local table when the
> policy routing rules are applied, but I'm not sure how.
> So far attempts to to do this have failed
>
> Has anyone managed to do this?
>
> Its more of a routing question so apologies for being slightly off topic.
>
> Best Regards
>
> Dean Scothern
> Dr Dean Scothern
> Infrastructure
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