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

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: [lvs-users] LVS-DR Cluster Some Real Servers Stuck in SYN_RECV
From: Bruce Rudolph <brudolph@xxxxxxxxxxx>
Date: Fri, 28 Feb 2014 15:01:26 -0500
I followed instructions from two sources

      1) 
http://www.centos.org/docs/5/html/Virtual_Server_Administration/s2-lvs-direct-iptables-VSA.html

                I updated iptables using the commands on this page.

      2) 
http://ptylr.com/2013/05/01/configuring-lvs-piranha-on-centos-for-direct-routing/

                This page had information on configuring lo:0 which was 
the final step that I needed to get LVS-DR to work.

The setup this way had been working since last August. It is still 
working on one of the real servers but not on four other ones. Very odd.



On 2/28/14 2:26 PM, Malcolm Turnbull wrote:
> 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@xxxxxxxxxxx> 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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>> http://www.linuxvirtualserver.org/
>>
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>
>

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