iRule to replace content of the location header on HTTP Responses

One of the potential issues I see with your current "contains" approach is that there is the possibility of a match on IP addresses other than 10.0.0.11 and 10.0.0.12, such as 10.0.0.110, 10.0.0.120, 110.0.0.121, 210.0.0.119, etc. All of these "contain" one or the other of the strings you're comparing against. (The likelihood of these other IP addresses actually appearing is probably remote, so you may be just fine.) To completely avoid an unanticipated match, you can make the "contains" strings more specific - maybe incorporate slashes into your matching strings - "/10.0.0.11/" and "/10.0.0.12/" (or maybe even something like ";) - but you would want to make sure you understand how the application always formats the Location header when it responds with an IP address instead of a host name.