This post is intended to be a general guide for configuring “stickied” load balanced HTTP servers. Whether it’s F5 load balancers, foundry load balancers or open source based load balancers (keepalived/lvs), the concepts are the same and can be migrated across said platforms.
If you have a paid of foundry’s and are looking to configure stickied load balanced HTTP servers, hopefully this guide will provide some assistance.
Logging into the load balancer
Telnet to the box and ‘enable’ to allow admin access. The first thing you want to do is show the current configuration to view the existing setup for other working boxes :
Real servers : defining the multiple load balanced boxes
Show the existing configuration on the foundary :
Take a look at the configuration of two “real” servers, which are the two servers that are behind the load balancer that will have balanced sticky connections :
The above example is balancing TCP 8001 traffic, which is for TOMCAT. Here are entries for two servers doing simple HTTP traffic :
This example is similar to the tomcat example, except you have several options. “port default disable” disables all other ports. “port http keepalive” and “port http url “HEAD /”” define the http checks that take place to ensure apache is running on that box. If not , it will fail over to the second box and stop sending traffic to it.
SSL incoming connections are handled by the load balancer initially, then passed off to the actual server as regular http / port 80 traffic. The internal box configuration would be similar to the above configuration examples :
Configuring the external IP to NAT to the internal virtual
Typically, you will have a firewall in front of the load balancer that actaully holds the external ip addresses. The traffic is filtered initially by the firewall, then NAT’d to the virtual ip (VIP) of the load balancer, which then handles balancing the traffic.
You will need to either establish a new external ip , or use an existing one (for instance, if you are moving from 1 web server to 2 web servers , and want to balance the traffic using the load balancer). You need to setup the external IP address, and NAT it to the internal VIP.
Verifying the configuration works
Once everything is setup properly, and the external IP is being NAT’d to the load balancer, it is time to ensure the load balancer is seeing the connections. You could do this before doing the switchover on the firewall as well, just to ensure everything looks right before actually doing the switchover.
To see the active connections being load balanced, issue the following command (replacing the servername for whichever one you want to check) :
That should display information similar to this :
The above is displaying the specific connection details for a single real server. To check the VIP / Virtual server :
Which will display the following :
You can see that “ServerConn” is displaying 46 connections. Thats it!