Red Hat ENTERPRISE LINUX AS 2.1 Installation Manual page 125

Section 8.2:Configuring Network Interfaces for a NAT LVS Cluster
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 sim-
ilar to this:
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=static
IPADDR=10.11.12.1
NETMASK=255.255.255.0
GATEWAY=10.11.12.10
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 clus-
tering, 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/syscon-
fig/network-scripts/ directory or by making sure the gateway
is correctly set in the interface which comes up first.
8.2.2 Enabling NAT Routing on the LVS Routers
In a simple NAT LVS cluster 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 7.5, 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 firewall marks, see Section 8.3, Multi-port Services
and LVS Clustering.
Note
WARNING
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