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Re: [lvs-users] CentOS/RHEL 6 ipvs issue with DR (different interfaces a

To: "LinuxVirtualServer.org users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] CentOS/RHEL 6 ipvs issue with DR (different interfaces and networks)
From: David Coulson <david@xxxxxxxxxxxxxxxx>
Date: Fri, 18 Oct 2013 07:07:24 -0400
On 10/18/13 12:50 AM, Alex Attarian wrote:
> You need to change the settings in order for IPVS DR to work if you have
> private and public networks or different networks on different interfaces.
> Those settings are:
> echo 2 > /proc/sys/net/ipv4/conf/default/rp_filter
> echo 2 > /proc/sys/net/ipv4/conf/all/rp_filter
>
> or if you would like to just do the interface where loadbalancer is sending
> traffic to, then:
> echo 2 > /proc/sys/net/ipv4/conf/<interface of real server ip>/rp_filter
>   (in my case eth1, so echo 2 > /proc/sys/net/ipv4/conf/eth1/rp_filter)
We have a large LVS environment with RHEL6 for both balancers and real 
servers. On most real servers we have rp_filter set to 1. Our network 
config is pretty much the same as yours (VIPs on lo, usually from a 
different subnet).

The only systems where we do have rp_filter set to 0 (I need to back and 
check why we picked 0 instead of 2 - 0 does work however) are systems 
which get packets from balancers using IPIP tunnels.
>
> Please note value of 1 does not have the same behavior on RHEL6 as it did
> on RHEL5.
Did you open a RedHat case on this behavior? Did they give you a BZ for it?

Not saying changing rp_filter wasn't the right thing to do, but I've not 
experienced a difference in how it functions in the last 12 years, 
including with RHEL6. On the few RHEL5 systems I have default rp_filter 
value is 1, so I'd expect them to behave the same.

David

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