[lvs-users] LVS-DR Cluster Some Real Servers Stuck in SYN_RECV

Malcolm Turnbull malcolm at loadbalancer.org
Fri Feb 28 19:26:43 GMT 2014

snip --  "I have setup
LVS-DR using IPTables."

Then why are you using a loopback adapter as well?

You only need to use one method iptables REDIRECT .... or ...
loopbackadapter + arptables settings

SYN_RECV means the real server is not replying when hit with a packet
that says Hi are you the VIP?

On 28 February 2014 19:21, Bruce Rudolph <brudolph at admantx.com> wrote:
> I have an LVS-DR cluster which has been running for seven months without
> a hitch. Recently, the cluster started to timeout on the majority of
> connections. Some connections were passed through to a real server and
> processed. I have tried for a week to figure out what happened. What I
> found was that one real server out of five is connecting and servicing
> the client request. The other four real servers have the HTTP connection
> stuck in the SYN_RECV state until it times out (60 seconds).
> In summary, I have seven CentOS 6.4 servers (kernel
> 2.6.32-358.18.1.el6.x86_64). Two servers are configured as load
> balancers (a primary and a backup) and five real servers. I have setup
> LVS-DR using IPTables. The servers have a public IP bound to a NIC
> device and an internal VLAN bound to a second NIC. The VIP is configured
> on the real servers local loopback (lo:0)  device. The
> /etc/sysconfig/ha/lvs.cf was setup properly and everything was running
> successfully for seven months.
> We installed new versions of our software for the web service we are
> running. Nothing network related. All five real servers were updated the
> same way. I am comparing the one working real server from the four that
> are not working. So far I have found nothing.
> Any ideas on trouble shooting points?
> --
> Best Regards,
> Bruce
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Malcolm Turnbull.

Loadbalancer.org Ltd.
Phone: +44 (0)870 443 8779

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