Installation guide

1.2. Routing on the Real Servers

The most important thing to remember when configuring the real servers network interfaces in a

NAT topology is to set the gateway for the NAT floating IP address of the LVS router. In this

example, that address is 10.11.12.10.

Note

Once the network interfaces are up on the real servers, the machines will be

unable to ping or connect in other ways to the public network. This is normal.

You will, however, be able to ping the real IP for the LVS router's private

interface, in this case 10.11.12.8.

So the real server's /etc/sysconfig/network-scripts/ifcfg-eth0 file could look similar to

this:

DEVICE=eth0

ONBOOT=yes

BOOTPROTO=static

IPADDR=10.11.12.1

NETMASK=255.255.255.0

GATEWAY=10.11.12.10

Warning

If a real server has more than one network interface configured with a GATEWAY=

line, the first one to come up will get the gateway. Therefore if both eth0 and

eth1 are configured and eth1 is used for LVS, the real servers may not route

requests properly.

It is best to turn off extraneous network interfaces by setting ONBOOT=no in their

network scripts within the /etc/sysconfig/network-scripts/ directory or by

making sure the gateway is correctly set in the interface which comes up first.

1.3. Enabling NAT Routing on the LVS Routers

In a simple NAT LVS configuration where each clustered service uses only one port, like HTTP

on port 80, the administrator needs only to enable packet forwarding on the LVS routers for the

requests to be properly routed between the outside world and the real servers. See Section 5,

“Turning on Packet Forwarding” for instructions on turning on packet forwarding. However, more

configuration is necessary when the clustered services require more than one port to go to the

same real server during a user session. For information on creating multi-port services using

Enabling NAT Routing on the LVS Routers