Change destination port based on hostheader

I wondered if I could use an irule to change the destination port of a standard http request based purely on the hostheader?

 

 

The current setup is as follows:

 

 

We are using BIG IP 9.4.4.

 

 

Standard http requests for multiple sites are sent to a single vserver, (DNS Aliases are used to conserve ip addresses). (Only port 80 is allowed for inbound traffic).

 

 

 

Is there an iRule that would acheive the following;

 

 

if the hostheader is URL_A the port should be changed to port 81 on any of the physical servers in the pool

 

 

AND

 

 

if the hostheader is URL_B then the port should be changed to port 82 on any of the physical servers in the pool.

 

 

 

Cheers

 

 

Jim