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xiaolche's avatar
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Feb 15, 2023

Collect UDP packet client IP with irule on LTM

Could anyone tell me how to collect client IP address with irule and save client ip to log ?

We have VIP which is for DNS and NTP service,  protocol profile is UDP  ( without Datagram LB enable) . i use below irule  in a  DNS VIP ( there is huge dns request to the vip ) , it worked for a few packets , then VIP stopped to response the dns request.   where is wrong on the irule ?  thanks for help in advance

log -noname local0. "[virtual name] client [IP::client_addr]:[UDP::client_port] test-snat [IP::local_addr]:[UDP::local_port] server [IP::server_addr]:[UDP::server_port]"




3 Replies

  • xiaolche Do you see any logs showing errors for that iRule after it was applied? Typically if something is wrong with the iRule you will see a log generated on your F5 to show what is causing the issue. If this is a virtual that is used a significant amount you could be logging too often which might cause your logs to exponentially increase in size but not just disable the one virtual server I don't believe. The syntax of that logging message seems to be correct but that is a significant amount of information that is being logged rather than just the client IP.

  • As per the doc here the command [IP::server_addr] is not available in the CLIENT_ACCEPTED event. I wonder how the iRule can succeed in some cases. As Paulius suggested you should see error messages if the iRule does contain errors. Can you check this? 

    • xiaolche's avatar
      Icon for Nimbostratus rankNimbostratus

      Thank you both.   I tried SERVER_CONNECTED first , then changed to CLIENT_ACCEPTED . So the log i saw maybe from server_connected. I will test again during maitenance window.