VPS Migration with OSPF

This article presents how to be able to migrate a container between different subnets in the network by using a dynamic routing protocol such as OSPF. An already working OSPF setup is mandatory, this article only shows the OpenVZ specifics.

Quagga installation

Install the Quagga routing suite available on the official website. For many distributions, a prebuilt package is available:

Under Debian:

apt-get install quagga

Under Gentoo:

emerge quagga

Under Fedora:

yum install quagga

Quagga configuration

In /etc/quagga/zebra.conf just put a password to be able to access the telnet interface.

password zebra

In /etc/quagga/ospfd.conf configure the OSPF network and area in which is OpenVZ server will be and configure the redistribution of routes generated by the container.

password zebra
!
router ospf
 redistribute kernel route-map only-ve
 network YOUR_NETWORK/XX area 0.0.0.0
!
route-map only-ve permit 10
 match interface venet0
!
line vty

Usage

Once your OpenVZ server takes part in the OSPF network, you can easily use the ‘vzmigrate’ command to migrate a container between different subnet of the network and the IP of the container will be redistributed in the whole network as a /32 (host route).

Bugs

To avoid problems with this setup the IP addresses of your container must be taken outside of any other subnet configured on your network. If the IP address of the container is taken from an actual subnet, the other hosts of the subnet won't be able to communicate with it, except if you use proxy arp on the router.