[lvs-users] Recursive SYN packets sent from Director to RealServer

Malcolm Turnbull malcolm at loadbalancer.org
Mon Aug 11 21:38:14 BST 2008


Its unlikely to be a bug.
Sounds like its related to the real server configuration.

Just a thought do you have more than one network card on the LVS box?
You're only blocking ARPs on eth0 at the moment.
Get DR working first and then move on to TUN (have you seen the recent posts
on MTU size?

2008/8/11 Calcote, Lee <lcalcote at pelco.com>

> Hi,
> We¹re having intermittent luck using LVS/TUN and LS/DR while trying to
> load-balance web services running on high port numbers: 10000, 60000, and
> 60001. To handle the ARP issue, we¹re using the hidden interface approach
> with the following sysctl settings on the real servers:
> > net.ipv4.conf.eth0.arp_ignore = 1
> > net.ipv4.conf.eth0.arp_announce = 2
> > net.ipv4.conf.all.arp_ignore = 1
> > net.ipv4.conf.all.arp_announce = 2
> > net.ipv4.conf.tunl0.arp_ignore = 1
> > net.ipv4.conf.tunl0.arp_announce = 2
> We find that client making HTTP requests at <VIP>:10000 (Webmin),
> <VIP>:60000 and <VIP>:60001 (both in-house web services) are able to
> successfully connect to real servers only intermittently. During failed
> requests, we find the Director is generating SYN after SYN request to the
> real server. The real server receives these (many thousand) SYN requests
> but
> sends no reply (SYN, ACK). One of the mysteries here is that at other times
> the same client will make a request and successfully connect to the web
> service. We¹ve test the load-balancing of SSH and had a 100% success rate.
> Does anyone know if this is a bug with LVS or have suggestions on what
> further troubleshooting may be done to identify the issue? Any help would
> be
> appreciated.
> Thanks,
> Lee
> -
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Malcolm Turnbull.

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

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