Using private IPs for Hardware Nodes

This article describes how to assign public IPs to VEs running on OVZ Hardware Nodes in case you have a following network topology:

Prerequisites

This article assumes you have already installed OpenVZ, prepared the OS template cache(s) and have VE(s) created. If not, follow the links to perform the steps needed.

Note: don't assign an IP after VE creation.

(1) An OVZ Hardware Node has the only one ethernet interface

(assume eth0)

Hardware Node configuration

Create a bridge device

[HN]# brctl addbr br0

Remove an IP from eth0 interface

[HN]# ifconfig eth0 0

Add eth0 interface into the bridge

[HN]# brctl addif br0 eth0

Assign the IP to the bridge

(the same that was assigned on eth0 earlier)

[HN]# ifconfig br0 10.0.0.2/24

Resurrect the default routing

[HN]# ip route add default via 10.0.0.1 dev br0

Note: if you are configuring the node remotely you must prepare a script with the above commands and run it in background with the redirected output or you'll lose the access to the Node.

A script example

[HN]# cat /tmp/br_add 
#!/bin/bash

brctl addbr br0
ifconfig eth0 0 
brctl addif br0 eth0 
ifconfig br0 10.0.0.2/24 
ip route add default via 10.0.0.1 dev br0

[HN]# /tmp/br_add >/dev/null 2>&1 &

VE configuration

Start a VE

[HN]# vzctl start 101

Add a veth interface to the VE

[HN]# vzctl set 101 --netif_add eth0 –save

Set up an IP to the newly created VE's veth interface

[HN]# vzctl exec 101 ifconfig eth0 85.86.87.194/26

Set up the default route for the VE

[HN]# vzctl exec 101 ip route change default via 85.86.87.192 dev eth0

Add the VE's veth interface to the bridge

[HN]# brctl addif br0 veth101.0

(Optional) Make HN(s) to be accessible from a VE

The configuration above provides following connections available:

VE X <-> VE Y (where VE X and VE Y can locate on any OVZ HN)
VE   <-> Internet
HN    -> VE

If you really need a VE to have an access to the HN(s) add an additional route rule:

[HN]# vzctl exec 101 ip route add 10.0.0.0/24 dev eth0

The resulted OVZ Node configuration

Making the configuration persistent (TODO)

A Hardware Node configuration can be done with help of ordinary initscripts configuration i suppose,
while VEs configuration will require creating additional script based on Making a veth-device persistent scheme.

(2) An OVZ Hardware Node has two ethernet interfaces (TODO)

(assume eth0 and eth1)