Irule with Multiple HTTP checks

A couple of suggestions:

If you have multiple services on the pool member being load balanced through the BIG-IP, it might actually be better to disable just the one service that is failing. Instead of using LB::down node 1.1.1.1, you could use 'LB::down pool member '. If the node is in multiple pools and you want to mark it down in all pools, you could use LB::down node 1.1.1.1 to mark it down in all pools.

You can make it slightly more efficient by not saving the command output to a variable:

This:

set n [IP::server_addr]
LB::down node $n

can be replaced with this:

LB::down node [IP::server_addr]

Likewise, this:

set r [HTTP::status]
log local0. "[IP::client_addr] -> [IP::server_addr] for the login page generated a HTTP $r response"

can be replaced with:

log local0. "[IP::client_addr] -> [IP::server_addr] for the login page generated a HTTP [HTTP::status] response"

Aaron