weird problems with my cluster.

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: weird problems with my cluster.
From: Nico Lumma <nl@xxxxxxxxxxxxxx>
Date: Mon, 28 Jan 2002 11:12:27 +0100

I am using a LVS-DR setup with a load-balancer (and one backup) and 6 realservers. All realservers are running a 2.4.16-SUSE kernel.

The setup is as follows:

All realservers have one internal IP (192.168.100.x) on eth0 and various real IPs on eth1, eth1:1, etc. (range from

The loadbalancer's MAC-address is statically set in the cisco router in order to avoid the arp-problem.

All realservers and loadbalancers are connected to one switch, which is connected to the gateway.

So far so good.

4 out of 6 realservers behave normally. They get the MAC-address of the gateway and happily route the packets to the gateway. 2 realservers, the 2 SMP-servers in my setup, behave rather strange. After a while they "forget" the MAC-address of the gateway and cannot recover it, even though all other realservers still have the right MAC-address. A tcpdump on the interface always leads to the same: the server is trying to send one ACK-packet to a client and is repeating this forever (I can't post the line at the moment because right now everything is fine). After a reboot everything is fine. The problem with this is, that ldirectord doesn't recognize that the realserver is hanging, since the httpd is still accepting connections on the internal IP-address. This leads the whole cluster to hang and makes me (and my boss) extremely unhappy. :(

Do you guys have any ideas what's going on? I had the same setup before but seperated both the internal and external interfaces on two switches, or rather switching hubs, and everything worked just fine. To get better performance I decided to go with the bigger switch and figured that the packets should be routed okay. Well, 4 out of 6 ain't bad, but I'd rather have all 6 servers working...

Thanks in advance,


Nico Lumma                                  nl@xxxxxxxxxxxxxx GmbH               
Borsteler Chaussee 55                       Tel: +49 40 46 85 67 - 20
D-22453 Hamburg                             Fax: +49 40 46 85 67 - 39

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