[vserver] How to ensure that host gets the primary ip address?

From: Thomas Gebhardt <gebhardt_at_hrz.uni-marburg.de>
Date: Wed 30 Jun 2010 - 08:35:39 BST
Message-ID: <4C2AF3CB.2000302@hrz.uni-marburg.de>

Hello,

somehow I got into the situation that the ip address of the Host is
secondary and a VServer gets the primary address:

# ip addr ls
...
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
state UP qlen 1000
    link/ether xx:xx:xx:xx:xx:xx brd ff:ff:ff:ff:ff:ff
-> inet <vserver1-ip>/24 brd <brdcast-ip> scope global eth0
    inet <vserver2-ip>24 brd <brdcast-ip> scope global secondary eth0
-> inet <host-ip>/24 brd <brdcast-ip> scope global secondary eth0
    inet <vserver3-ip>/24 brd <brdcast-ip> scope global secondary eth0
    ...
...
4: vlan71@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue
state UP
    link/ether 00:04:23:d6:b4:a8 brd ff:ff:ff:ff:ff:ff
    inet <vserver6-ip>/25 brd <brdcast2-ip> scope global vlan71
...

* I have the sysctl setting "net.ipv4.conf.all.promote_secondaries=1",
so the host will not get offline when I shutdown vserver1.
* The hostname of the host resolves to host-ip.

Nethertheless, ssh connections from the host get vserver1-ip as its src
address, obviously because vserver1-ip is the primary ip address of the
eth0 interface. I can fix this by the BindAddress directive in
ssh_config, but this is just a workaroud for ssh and I don't know
whether other services will be affected, too. A much cleaner solution
would be to "pin" the primary role to the host ip.

Any idea how to achieve that and/or how to swap the primary and
secondary role of the ip adresses in my current situation?

Thanks, Thomas
Received on Wed Jun 30 08:36:32 2010

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