Yealink voip phone Busy Lamp Field

[janelle.provine]

I have a palo alto 220 on OS 10.1 and recently put in yealink phones that access the phone servers through our ISP. Everything works except for a function called 

Busy Lamp Field (BLF)

BLF is an acronym for Busy Lamp Field, which is a light on an IP Phone or a colored indicator next to a name in a softphone or web client, that tells you whether another extension connected to the same PBX is busy or not. Many popular IP phone manufacturers, such as Yealink, Fanvil and Snom, sell a variety of phones that have BLF function keys.

The ISP believe there is something on the PA that is blocking this function and I need to find what and how to allow it access. 

[Claw4609]

Is anything showing at blocked in the traffic, url, or threat logs when you filter by either the source or destination?

If nothing is explicitly being blocked but its still believed the issue is the firewall a good next step would be checking counters. How to check global counters for a specific source and destinat... - Knowledge Base - Palo Alto Netw...

[janelle.provine]

nope nothing showing blocked anywhere

[janelle.provine]

I ran lots of packet captures and it didn't show anything blocked either

[janelle.provine]

This is all the drops I am currently showing

ame value rate severity category aspect description
--------------------------------------------------------------------------------
flow_rcv_dot1q_tag_err 90 3 drop flow parse Packets dropped: 802.1q tag not configured
flow_no_interface 90 3 drop flow parse Packets dropped: invalid interface
flow_fwd_l3_mcast_drop 5 0 drop flow forward Packets dropped: no route for IP multicast
flow_host_service_unknown 4 0 drop flow mgmt Session discarded: unknown application to control plane
--------------------------------------------------------------------------------
Total counters shown: 4

[Claw4609]

If you are not seeing anything blocked I would verify with the ISP what IPs and ports are used for BLF to ensure those connections would be allowed.

[janelle.provine]

Well since its their servers and their phone system I believe so already worked with the ISP directly, the took the firewall out of the mix and it started working but I have no idea where else to look

[BDent]

Did you ever find a resolution to this issue? I am having the same issue with Polycom phones on a Broadcom PBX