topic Bytes received zero for allowed udp ports in General Topics

Bytes received zero for allowed udp ports

DhananjayBhakte — Tue, 15 Jun 2021 15:18:57 GMT

Hi,

In traffic allowed logs, I am seeing numbers in byte sent however byte received is zero and connections are getting aged-out for UDP voice traffic.

Can anyone know about such traffic whether it is dropping or since this is UDP connection hence byte received is zero

This traffic is allowing via security policy configured for outside to inside NAT, NATED IP is of cisco meraki server.

Thanks

Dhananjay Bhakte

Re: Bytes received zero for allowed udp ports

Remo — Sat, 03 Jul 2021 22:24:24 GMT

Hi @DhananjayBhakte

These are just sessions that are allowed but don't have any reply. Allowed UDP sessions always have the session end reason aged out as this protocol is stateless. There isn't a packet like FIN or RST packet in TCP, so the firewall applies a timeout after a udp packet and if there is no answer or another UDP packet for the same session, this session will be removed from the session table after this timeout is reached and the session is then displayed as aged-out in the logs.

Re: Bytes received zero for allowed udp ports

DhananjayBhakte — Mon, 05 Jul 2021 03:31:33 GMT

Thank You Vsys_remo for reply,

Yes I agree with you, later I saw applications are discovering in same traffic logs, those applications was SIP other voice related applications and these applications always runs on UDP protocol since it is connection less protocol I was getting bytes received zero and aged-out.

Thanks

Dhananjay Bhakte