syslog udp session keep alive ?

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syslog udp session keep alive ?

L0 Member


When forwarding logs, they are being sent to udp 514. The udp time out is 30 seconds, and the syslog server actually receives packets every 5 seconds. However, I wonder why the firewall keeps the session longer than 30 seconds. When the time is long, it is several minutes or hours, and sometimes the date passes.



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Cyber Elite
Cyber Elite


Its because they are UDP packets/sessions. Here is an article from Palo Alto on this:


When monitoring the traffic logs using  Monitor > logs > Traffic, some traffic is seen with the Session End Reason  as aged-out.  Any traffic that uses UDP or ICMP is seen will have session end reason as aged-out in the traffic log. This is because unlike TCP, there is there is no way for a graceful termination of UDP session and so aged-out is a legitimate session-end reason for UDP (and ICMP) sessions.



Cyber Elite
Cyber Elite

If you add "From port", "Packets sent" and "Packets received" columns you can see that until syslog sender is sending traffic from same source port Palo keeps same session open and packets are gathered under same session. 

If no new packets in this session for 30 seconds then this session is closed.


Enterprise Architect, Security @ Cloud Carib Ltd
Palo Alto Networks certified from 2011
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