Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

Forum Discussion

Amar_A_361783's avatar
Amar_A_361783
Icon for Nimbostratus rankNimbostratus
May 18, 2018

Configuring LB VIP With backend server with different set ports

Hi All, I need to setup a LB vip. In this setup i have a vip that would be listening on some random port(ex:-65001). There are backend server are using different ports(ex:-65002,65003).   To sumar...
application delivery
irules
LTM
youssef1's avatar
youssef1
Icon for Cumulonimbus rankCumulonimbus
May 18, 2018

Hi Amar,

 

To resume you will have an VIP that will listnen on random port:

 

VIP: IP:*

 

With the following backend:

 

  • SrvA:65002
  • SrvA:65003
  • SrvB:65002
  • SrvB:65003

TMM will perform destination address and port translation when load balancing to a pool. This is enabled by default and configurable using the address and port translation settings on the virtual server properties.

 

SO to resume, F5 will LB to a pool depending LB setting then translate your dest port to the pool memeber dest port:

 

example: https://1.1.1.1:65002

 

  • If F5 LB your request to SrvA:65003, F5 will translate your dest port to 65003.

     

  • If F5 LB your request to SrvA:65002, F5 will translate your dest port to 65002 (it is the same).

     

can you clearly explain your need I can help you implement it!!!

 

Just for information if you uncheck in VS settings "translated port" the request port done by client is use in memember pool. If user enter https://1.1.1.1:65002 the server will manage the request on port 65002 even if he has another port defined on poolmemeber...

 

Regards