Forum Discussion

shaikhzaid's avatar
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Jan 03, 2023

virtual server config

hey guys,

i have a requirement wherein the url will be accessed over the internet.

Now once the NATing is done by the firewall, the traffic will be passed to virtual server ( with client and server ssl profiles applied. Now the question is do i need to apply the pool with server:port ( under the resource tab of the VS?

Also the virtual server destination port should be 443 or 9999 ?

I am confused here. any help will be appreciated .

  • CA_Valli's avatar
    Jan 03, 2023

    Well, this is up to you. 
    Per my experience, some customers prefer to offload the SSL decryption task to the F5 unit, so that they don't have to perform additional decriptyon on the backend server farm, saving resources. This is usually also allows more agile administration, because you'll only need to renew the certificates on one appliance (BIG-IP) instead of every server. 
    Other customers prefer to perform SSL encryption in the backend as well because they prioritize information security across the whole network. 

    You might want to discuss this with your engineering team, and if your servers require the SSL handshake to be performed, you'll need a serverSSL profile. 

11 Replies

  • Hello,

    First, the virtual server port is usually same port which the client is requesting. For example, if your request is "" so you can configure the virtual server with the natted IP that the firewall forwards the traffic to and the port is "9999".

    Regarding the pool member ports, it depends on what port the server is listening on and expecting to receiving traffic on. as F5 by default is having port translation enabled in the virtual server configuration, so you can either configure the pool member port with 443 or 9999 depending on the server itself.

    Feel free to raise any questions.


    Mohamed Salah.

  • If the client requests the URL specifying a destination port, which is :9999 syntax, your network equipment should be configured to accept connections to that port.

    You say there's a firewall that performs NAT translation, so I'd guess this is the first access block. Does it translate port from 9999 to 443 as well? (I'm assuming this since you say VS is configured for port 443)

    If it doesn't, you need to have a Virtual Server configured with destination port 9999 (again, since this is specified in cliet request) and with tcp, http, and clientSSL/serverSSL profiles. 

    BIG-IP is a default deny device, so any client request that does not meet this criteria (= there's not a listener configured) will be rejected. 

    F5 keeps client- and server- connections separate, so if you need to change port before going to the backend server you can do it. Pool configuration should match the port configured in your server farm to listen for this connection / to serve this application. 

    • shaikhzaid's avatar
      Icon for Altocumulus rankAltocumulus

      Thank you guys for the swift response.

      I have configured the firewall to translate only the public ip to VIP on F5. 

      On the virtual server config, it is listening on port 443, and the pool called-in this VS is pool with port 9999.

      Also both client and server ssl profiles are applied.

      on the firewall am getting TCP reset from server.

      • CA_Valli's avatar
        Icon for MVP rankMVP

        Ok, based on this information I'm expecting the reset to be on port 9999, and this is because port 9999 does not match your virtual server socket. 

        Virtual Server should match the port specified in client connection, so you need to change it to listen on port 9999.

  • Hello shaikhzaid,

    If you are translating the IP only, you should change the virtual server port to the requested port from the client which is "9999" because as Cali mentioned, F5 is a deny by default device. and since there is no virtual server configured with port "9999" the traffic will be denied.

    take a look at the configuraiton again.


  • srir's avatar
    Icon for Nimbostratus rankNimbostratus


    Below is my setup.

    Oauth provider -mapped to- Oauth Server

    Oauth server > mapped to -- APM policy

    APM policy > mapped to -- Virtual server

    Virtual server > mapped to pool

    All components looking good. When i tirgger the SSO enabled URL it never loads APM policy..

    any inputs appreciated