So I have a content switch module in one of my switches. It's used for Load Balancing of services across multiple servers. Think multiple servers for 1 web page, all the servers are mirrored so you get the same content, it just spreads the pain around to 4 servers instead of having 1 server to do all the work.
So I'm renumbering 4 of the servers. We're actually upgrading some of the content to virtual servers, but leaving some stuff behind on the old server. It was a case of a new product not having a home and sharing the load on the servers, with out creating a virtual server.
Anyway like I said, renumbering servers. Set up the firewall to point the traffic to the load balancer. Set the server up to pass traffic. I already have one up and running this is the second one. I spent roughly 2 to 3 hours trying to figure out why this thing couldn't get a network connection. It could talk to the other servers on the same vlan / network, but moving across to the other vlans and networks (where the firewall comes into play) it wouldn't.
Change ip addresses, same problem. Change gateways to the DMZ instead of the LB, and it would get a net connection. Double check the firewall routing. It still didn't work.
Then I thought, ok, the only thing I haven't done is put it into a server farm yet, on the CSM. As soon as I did that, it started working. Why the LB, needs to know what server farm something belongs to before it starts passing traffic I have no idea. I think it's a bad design though. I can see why they'd do it that way. That way you don't have things pointing to the load balancer that aren't being balanced. But when you're just setting up a box, you don't want it to be balanced, you want it to work.