The Usual Tech Ramblings

F5 and Passive Host Monitoring

Lori MacVittie has an excellent article on passive host monitoring in an F5 Big-IP environment. Introduced in v10, BIG-IP load balancers now support something called Inband Monitoring. This basically sniffs the traffic, and responds based on the rule you define. Lori put an example up which looks for the HTTP error codes above 500, and after 3 errors seen in the responses, it marks that host as unavailable. This is a great feature as it doesn’t add any load to the web servers with active checks, and if you have ever looked at a host that i s behind a load balancer, log analysis can be a pain. The cool thing is, after the host has been disabled, the passive check can enable your regular active checks to bring the host back up when the issue is resolved. Some excellent stuff.