3.3. Putting the Configuration Together

After determining which of the preceding routing methods to use, the hardware should be linked together on the network.

Important

The adapter devices on the LVS routers must be configured to access the same networks. For instance if eth0 connects to public network and eth1 connects to the private network, then these same devices on the backup LVS router must connect to the same networks.
Also the gateway listed in the first interface to come up at boot time is added to the routing table and subsequent gateways listed in other interfaces are ignored. This is especially important to consider when configuring the real servers.
After physically connecting together the hardware, configure the network interfaces on the primary and backup LVS routers. This can be done using a graphical application such as system-config-network or by editing the network scripts manually. For more information about adding devices using system-config-network, see the chapter titled Network Configuration in the Red Hat Enterprise Linux Deployment Guide. For the remainder of the chapter, example alterations to network interfaces are made either manually or through the Piranha Configuration Tool.

3.3.1. General Load Balancer Add-On Networking Tips

Configure the real IP addresses for both the public and private networks on the LVS routers before attempting to configure Load Balancer Add-On using the Piranha Configuration Tool. The sections on each topology give example network addresses, but the actual network addresses are needed. Below are some useful commands for bringing up network interfaces or checking their status.
Bringing Up Real Network Interfaces
To open up a real network interface, use the following command as root, replacing N with the number corresponding to the interface (eth0 and eth1).
/sbin/ifup ethN

Warning

Do not use the ifup scripts to open any floating IP addresses you may configure using the Piranha Configuration Tool (eth0:1 or eth1:1). Use the service command to start pulse instead (see Section 4.8, “Starting the Load Balancer Add-On” for details).
Bringing Down Real Network Interfaces
To bring down a real network interface, use the following command as root, replacing N with the number corresponding to the interface (eth0 and eth1).
/sbin/ifdown ethN
Checking the Status of Network Interfaces
If you need to check which network interfaces are up at any given time, type the following:
/sbin/ifconfig
To view the routing table for a machine, issue the following command:
/sbin/route

3.3.1.1. Troubleshooting Virtual IP Address Issues

There may be instances when an administrator encounters issues during an automatic failover from an active LVS host to the standby host. All of the virtual IP addresses may not activate on the standby host upon failover. This issue can also occur when the standby host is stopped and the primary host is activated. Only when the pulse service is manually restarted do all virtual IP addresses activate.
To remedy this issue temporarily, you can enter the following command at the root shell prompt:

echo 1 > /proc/sys/net/ipv4/conf/all/promote_secondaries
Note that this will only temporarily remedy the issue and that the command will not hold through a system reboot.
To permanently remedy this issue, open the /etc/sysctl.conf file and add the following line:
net.ipv4.conf.all.promote_secondaries = 1