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TFleming's avatar
TFleming
Icon for Nimbostratus rankNimbostratus
Apr 17, 2020

Find connection attempts via source IP

Hey guys, I'm fairly new to F5. We have one configured before I started working here. We have a windows terminal server virtual server in our F5 that load balances between 18 different back end termi...
application delivery
BIG-IP
devops
TMSH
  • Beaker's avatar
    Beaker
    Apr 20, 2020
    when CLIENT_ACCEPTED {
  set LogString "Client [IP::client_addr]"
  log local0. "==== $LogString (request) ====="
}
 
when SERVER_CONNECTED {
  log local0. "==== $LogString (server connected) - server: [LB::server addr]:[LB::server port] ===="
}

    I have tested that this works

Beaker's avatar
Beaker
Icon for Cirrus rankCirrus

You can accomplish this with an Irule on the VIP that would log the connections and output them into the ltm log.

Something like this should help with troubleshooting. But I would only use while troubleshooting not as a permanent addition:

when HTTP_REQUEST {
  set LogString "Client [IP::client_addr]:[TCP::client_port] -> Requested Host[HTTP::host][HTTP::uri]"
  log local0. "==== $LogString (request) ====="
}
 
when SERVER_CONNECTED {
  log local0. "==== $LogString (server connected) - server: [LB::server addr]:[LB::server port] ===="
}
 
when HTTP_RESPONSE {
  log local0. "==== $LogString (response) - status: [HTTP::status] ===="
}
TFleming's avatar
TFleming
Icon for Nimbostratus rankNimbostratus
Apr 17, 2020

Great thank you! One quick question because I don't want to make any assumptions, will this cause an outage of any kind? Will I need to restart anything to have he iRule work?

  • Beaker's avatar
    Beaker
    Icon for Cirrus rankCirrus
    Apr 17, 2020

    This should no impact on actual traffic as all that is happening is the F5 is logging details of the connection. Depending on the traffic load it could lead to a lot of entries in the ltm log but that is why it is recommended for troubleshooting not permanent use.

  • TFleming's avatar
    TFleming
    Icon for Nimbostratus rankNimbostratus
    Apr 17, 2020

    Great thank you!