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Mr__T's avatar
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Sep 19, 2023

Replace server name

Hello All,

I am looking to replace the FQDN of a URL with the server name keeping the remainder of the URL after the FQDN. Trying to find the simplest way to acheive this. Dont want to redirect the entire URL, just swap the FQDN.

5 Replies

  • Hi Mr__T so you are just wanting to rewrite the Host header in the communication from client->BIG-IP->server, but not issue a redirect, correct? You can do that in an LTM policy or in an iRule.



    ltm policy host_rewrite {
        last-modified 2023-09-19:14:47:44
        requires { http }
        rules {
            host_rewrite_all_traffic {
                actions {
                    0 {
                        name Host
        status published
        strategy first-match




    when HTTP_REQUEST priority 500 {
        HTTP::header replace host ""


    Note that this is not rewriting the location headers being returned from the server, and is assuming they are a) returning the original fqdn and b) are fine receiving a rewritten host. If that's the not the case, you'll need to do some more work. Post back with more details if necessary. HTH...Jason

  • Is one of the requirements to rewrite the request differently depending on the pool member chose. during the LB selection? For example, if you have 2 origin servers, they probably have unique names. So the rewrite may have to match the server that is selected on the server side of the connection.

    • Mr__T's avatar
      Icon for Cirrus rankCirrus

      Correct, 2 servers that can't use FQDN. Wont be LB per say more like failover. 

  • note: 

    pool member is selected after the first http request.  you need to forces the selection.  if you planning "if pool member x then host names y" 

    or create two pools.   once for each FQDN name.   "if (pool 1 no members) then (host name y + user pool 2) else (host name x)"