Forum Discussion

Jaspreetgurm's avatar
Icon for Altocumulus rankAltocumulus
Oct 29, 2021

Virtual Server Log Forward to Splunk

I want to setup log forwarding from F5 to splunk server for https traffic of one of virtual server.


Below needs to be capture from traffic and send to splunk server.


Domain Name

Source IP

Http Version

Target IP

http status

time taken


5 Replies

  • You'll have to modify your hsl cmd to avoid outage, there's a known bug & I learned it by experience. Hope it helps.

    Also why would you need a TCP, set it as UDP protocol.

    set client_address [IP::client_addr]
    set vip [IP::local_addr]
    #Set the splunk hsl pool in a variable first
    set splunk_pool Splunk_HSL_Pool
    #Use that variable to call out in below command
    #Bug -
    set hsl [HSL::open -proto UDP -pool $splunk_pool]

    And again i see you are creating an HSL open in HTTP RESPONSE which is not required. Just HSL send would be enough.

  • You can do that with HSL, all the pieces you need are in this article. Post back with some code fragments if you have any questions and we'll help you out!

    • Jaspreetgurm's avatar
      Icon for Altocumulus rankAltocumulus

      Thanks, Jason :)


      I just prepared the configuration as below. Please revert with your kind suggestion on this.




      1) Adding Splunk server as pool member.


      Navigate to Local Traffic > Pools


      Click Create.




      IP address :-

      Port    :-514


      Click Finished.


      2) Log Destination


      Navigate to System > Logs > Configuration > Log Destinations .


      Click Create.


      Name field :- Splunk_HSL_logging

      Type:- Remote High-Speed Log


      Pool Name :- Splunk_HSL_Pool


      Protocol :- HSL


      Click Finished.


      3) Log Formatt


      Navigate to System > Logs > Configuration > Log Destinations .


      Click Create.


      Name:- Splunk_Logs


      Type:- Splunk.


      Forward To :- Splunk_HSL_logging


      Click Finished.


      4) Publisher


      Navigate to System > Logs > Configuration > Log Publishers .


      Click Create.


      Name :- Splunk_Publisher


      Destinations :-Splunk_HSL_logging.


      Click Finished.



      Irule for virtual Server.



      Goto->Local Traffic-Irule

      Name:- Splunk_logging


      Copy paste below code.


      when CLIENT_ACCEPTED {

       set client_address [IP::client_addr]

       set vip [IP::local_addr]

       set hsl [HSL::open -proto TCP -pool Splunk_HSL_Pool]


      when HTTP_REQUEST {

       set http_host [HTTP::host]:[TCP::local_port]

       set http_uri [HTTP::uri]

       set http_method [HTTP::method]

       set http_version [HTTP::version]

       set virtual_server [LB::server]

       set http_user_agent [HTTP::header "User-Agent"]

       set http_content_type [HTTP::header "Content-Type"]

       set tcp_start_time [clock clicks -milliseconds]

       set req_start_time [clock format [clock seconds] -format "%Y/%m/%d %H:%M:%S"]

       if { [HTTP::header Content-Length] > 0 } then {

         set req_length [HTTP::header "Content-Length"]

       } else {

         set req_length 0



      when HTTP_RESPONSE {

      #  set res_start_time [clock format [clock seconds] -format "%Y/%m/%d %H:%M:%S"]

       set node [IP::server_addr]

       set node_port [TCP::server_port]

       set http_status [HTTP::status]

       set req_elapsed_time [expr {[clock clicks -milliseconds] - $tcp_start_time}]

       if { [HTTP::header Content-Length] > 0 } then {

         set res_length [HTTP::header "Content-Length"]

       } else {

         set res_length 0


      set hsl [HSL::open -proto UDP -pool Splunk_HSL_Pool]

      HSL::send $hsl "<514> HSL, CLIENT_IP=$client_address, VIP=$vip, VIP_NAME=\"$virtual_server\", SERVER_NODE=$node, SERVER_NODE_PORT=$node_port, HTTP_URL=$http_url, HTTP_VERSION=$http_version, HTTP_STATUS=$http_status, HTTP_METHOD=$http_method, HTTP_CONTENT_TYPE=$http_content_type, HTTP_USER_AGENT=\"$http_user_agent\", HTTP_REFERRER=\"$http_referrer\",REQUEST_START_TIME=$req_start_time,REQUEST_ELAPSED_TIME=$req_elapsed_time, BYTES_IN=$req_length, BYTES_OUT=$res_length\r\n"






      • Kalido's avatar
        Icon for Altostratus rankAltostratus

        Hi Jaspreet,

        Amazing Instructions above, I followed it step by step thank you for the easy guide.


        Can I ask did the above work for you? was you able to get logs regarding your virtual server? 

        I.e connectivity etc ?

        I am looking on Splunk and I can find any good data ?

  • I followed the above steps and configured the iRule however when I am applying the iRule the virutal server stops working,  getting message " This page isn’t working". I captured the traffic on LTM but don't see any issue.

    Any help is greatly appreciated. Thanks!