topic syslog udp session keep alive ? in General Topics

syslog udp session keep alive ?

kimjeonghoon — Thu, 29 Dec 2022 05:38:11 GMT

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.

Re: syslog udp session keep alive ?

OtakarKlier — Thu, 29 Dec 2022 21:09:04 GMT

Hello,

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.

https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000PMjLCAW

Regards,

Re: syslog udp session keep alive ?

Raido_Rattameister — Fri, 30 Dec 2022 16:51:04 GMT

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.