proxy to node based on hostname

First time posting here.

I wanted to know if anyone had an idea on how to proxy to a node/server based on hostname rather than IP. I thought maybe an iRule could be used instead of a traditional resource pool with members.

We are proxying to a server that is not managed by us. We need to preserve the hostname and the server on the backend expects that hostname so redirects will not work.

We cannot just use DNS for there are many links our users use with short names to this service (hostname rather than hostname.domain.com) and the backend server does not have our DNS server suffix within its configuration therefore cannot match the FQDN host when we send a request to it using just a DNS CNAME.

Therefore we use the LTM to convert the short name to a FQDN and then proxy the request back to the host that we do not manage. This works well except for one thing, the bigip.conf configuration saves the member as an IP, not a hostname. If the vendor changes the IP of this server, we will no longer be able to proxy to it unless we update the configuration.

I thought I could write an iRule which does a proxy based on hostname

For example:

when RULE_INIT {

Set the hostname that the client makes request to

set external_hostname "something.domain.com"

Set the hostname that the BIG-IP will proxy requests to

set internal_hostname "asp.otherdomain.com"

}

when HTTP_REQUEST {

if { [string first "." [HTTP::host] }] < 0 && [string length [HTTP::host]] >= 1} {

set host "[HTTP::host].domain.com"

HTTP::redirect "http://$[HTTP::host]$[HTTP::uri]"

}

if { [HTTP::host] == ${external_hostname} } {

proxy to internal hostname

SOMETHING "${internal_hostname}[HTTP::uri]"

}

}

where SOMETHING proxies to the server we do not manage (not redirect).

Any help is appreciated. C