[lvs-users] LVS Setup interfering with connection to other server?

To: "' users mailing list.'" <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: [lvs-users] LVS Setup interfering with connection to other server?
From: "Dan Brown" <danb@xxxxxx>
Date: Sat, 28 Jun 2008 09:11:07 -0600
I have a server which I recently migrated a number of sites to and
subsequently could not connect to a mail list server running mailman after
doing the move.   The problem appears to be caused by the new server
although I can't figure out why.  I discovered that when the new server is
up and running:

1. The maillist server itself cannot reassign itself it's IP address.  I
restarted the network interfaces and I get the following:
[root@iris rc.d]# /etc/init.d/network restart
Shutting down interface eth0:                              [  OK  ]
Shutting down interface eth1:                              [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Setting network parameters:                                [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  Error, some other host already uses address
Bringing up interface eth1:                                [  OK  ]

Awesome eh?  As it happens, the router says the MAC address it is the same
as the server it is supposed to be, even after rebooting the router.  Why
would the new server be arp'ing for a server it has no configuration for?

If I assign the interface using:

ifconfig eth0 netmask broadcast

it comes up normally.

2. The new server is part of the LVS system and has a couple of hundred IPs
on its loopback interface (via DR for, and,
the real IP is on the network block  It cannot connect
to the server in problem 1 when those IPs are in place.  When the address is
assigned, no other servers (almost all part of the LVS) have any problems at
all connecting to it.  Just this one server.  Originally it had some
arptable rules about not responding to that IP address but that has since
been removed.  It has never had a loopback entry for the IP itself.  The IP
of the server itself is on a different network but it's all behind the same
router.  The server is:, the maillist server is 

For some reason, it appears the server is connecting to itself.  A tcpdump
on the loopback address shows:
08:15:24.808782 IP > S
1356583672:1356583672(0) win 32767 <mss 16396,sackOK,timestamp 50190198
0,nop,wscale 2>
08:15:24.909467 IP > R 0:0(0)
ack 1356583673 win 0

None of the other LVS real servers I've setup are having this problem, and
there are no problems connecting to any of the sites on the server...  so
what did I miss this time?

Dan Brown

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