Help with Irule to forward traffic

In order to answer your question there are several assumptions that need to be made.

1. The default route on the LTM points towards the firewall or router that points you our to the internet.

2. Your client has to be able to route towards the VIP somehow either through your network.

3. VIP 0.0.0.0:80 at the minimum.

4. You may need may need SNAT or AUTOSNAT if the clients gateway isn't the LB.

Your IRULE could look like this, applied on the VIP 0.0.0.0:80

when HTTP_REQUEST {
  if { [HTTP::uri] equals something]} {
    forward
  } else {
    pool pool_name
  }
}

You could also use the SWITCH Command, references can be found on the following link so Click here

I have never tried this particular way of forwarding but that may be the logic you want to go with.