Change Host Value

I've seen in other posts that you can set the host itself with the HTTP::host command, though it doesn't appear to be supported in my version (9.1.2)

when HTTP_REQUEST {
  if { [HTTP::host] equals "www.outsidedomain.com" }{
    HTTP::header replace host "servername"    HTTP::host "servername"
    log local0. "The header is [HTTP::header host] "
    log local0. "The Host Value is [HTTP::host]"
  } else {
    log local0. "No Changes Made"
  }
}

I also thought 'HTTP::host mynewhost.example.com' would work, but it doesn't on 9.2.3 either.

I think the value of HTTP::host is cached so you don't see the updated value when setting the host header value with 'HTTP header replace Host newhost.example.com', but the value is actually changed. [HTTP::header Host] apparently isn't cached and therefore shows the correct value.

Regardless, you should be able to confirm by checking the HTTP data sent from the BIG-IP to the node using tcpdump or looking at the node's web server logs.

As for rewriting the responses:

If the web application is sending absolute references which include the internal domain, you could use a stream profile to rewrite oldhost.example.com in the HTTP content.

If you need to rewrite the domain in redirects, you could use a rule (the stream profile won't operate on HTTP headers). Here is an example:

when HTTP_RESPONSE {
   if {[HTTP::is_redirect]}{
      HTTP::header replace Location [string map { "oldhost.example.com" "newhost.example.com" } [HTTP::header value Location]]
   }
}

Aaron