BIG-IP BGP Routing Protocol Configuration And Use Cases

Well hello there Michael and thank you for stumbling on my article. I had the intention to write more of the series, but as there really wasn't a lot of feedback I didn't think anyone really wanted to hear from me. My goal was to cover how HA behavior works with BIG-IP and BGP in the second in the series. And well, your questions inspired me to pick this back up.

But to quickly summarize. If a BIG-IP HA-Pair is set up properly the kernel routes should only show up in the routing table IF the BIG-IP is active. The standby for the traffic-group will not have the kernel routes to redistribute.

This is why, in my lab which you also stumbled upon; I use aggregate-address. BGP is a different routing protocol in that it generally must learn a route from another routing protocol, or static, or in this case from the kernel. Without the /32 kernel route for the BGP process to learn something in the /24 aggregate it won't advertise the /24. This would leave me to believe that the /32 is active in the kernel on both devices which is why you saw it advertised from both.

One fun fact. When you use aggregate-address it will install a /24 route to null0 in the routing table to advertise. This is also why if there are individual VIPs in the range they all should have advertisement enabled assuming you don't want the route withdrawn if any particular /32 fails.