F5 LTM VE – Setting up basic load balancing

In this post we are going to go through setting up basic load balancing.  On the LTMs this is a relatively easy task so I’m going to rip right through it.  The nice thing about the configuration is that instead of starting from the bottom up, you can actually start from the top down.  So rather than creating all of your nodes, then creating the members, and then the pool, we can just start with the virtual server and add the other objects.  Best shown by example, so here we go..

Log in to your VE LTM and blow up ‘Local Traffic’ on the left menu bar.  Select the ‘’Pool’ option and on the far right select the ‘Create’ button.

On the next screen, give the pool a name, select ‘http’ for the health monitor, and then move down to the resources area.  Enter the information for each of your web hosts into the ‘New Members’ area.  Enter 1’s info, then hit add, etc. until all of them are listed in the text box as shown below…

Then click ‘Finished’ to create the pool.  You should now see your pool created and it should have a pretty green circle next to the name indicating that the monitors are succeeding in querying the device on port 80.

 
Now that the pool is created, we need to create a virtual server to associate it with.  Select ‘Virtual Servers’ from the ‘Local Traffic’ menu on the left hand side of the screen.  Then click the ‘Create’ button on the far right of the window.

 
There are lots of options on the next screen but just concern yourself with the ‘General Properties’ window.  The ‘Destination’ field is the IP of the VIP that clients will connect to in order to be load balanced.  Fill in your relevant information as shown below…

 
Then scroll to the bottom and click ‘Finished’ to create the virtual server.  Once the server is created, it will take you back to the main virtual server window.  Click the ‘Edit’ link on the far right of the virtual server description under resources…

 
Under ‘Default Pool’ select your newly created pool and then click ‘Update’

 
At this point we are ready to test.  Open up a web browser and point it to the VIP.  http://10.20.20.21 and see what you get.  Hopefully, you’ll get nothing.  Why do you ask?  Because the web servers are returning traffic to our default gateways, not the LTM.  Open up the virtual server settings and change the ‘SNAT Pool’ setting from ‘None’ to ‘Automap’.  Automap tells the LTM to change the source to one of its self IPs in that subnet.  In this case, it would source the packets from the 192.168.1.40 address. 

Once the SNAT pool is specified, try hitting the VIP again and see what happens.  With any luck you should get one of the web servers.  Three refreshes and you should see all of the web servers get hit as shown below…

 
So that is all it takes to setup a very simple load balancing configuration.  Not hard right?  In the next post, we’ll go back through and talk a little bit more about what we just set up as well as look at monitors.