Bytes received zero for allowed udp ports

[DhananjayBhakte]

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

[Remo · Accepted solution]

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.

[DhananjayBhakte · Accepted solution]

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