Polycom phone goes Unreachable

We have a number of Polycom phones at a remote site and I am seeing ONE phone become Unreachable periodically throughout the day. There are multiple phones of the same model but only this one seems to be a problem child while others seem to stay connected.

We are using PJSIP and I have done logging. I see the SIP OPTIONS packet sent and responded to every minute and then BAM the phone just stops responding. I have to think firewall config and internet connection are OK since other phones at the same site continue to respond correctly during the same time intervals and appear to work fine making/receiving calls.

I have been able to identify one thing which so far seems consistent when the phone stops responding. It looks like the phone was always on a call that was terminated less than a minute prior to when it stops responding to OPTIONS commands. From the PBX side it looks like it goes through normal call hangup but maybe the phone doesn’t know the call has been terminated?

Anyone seen this behavior before? This is on FreePBX And yes, we using older Polycom phones (430’s). The phones could be upgraded if this is the problem but I am looking for some concrete explanation before I start doing random things to address.

VLANs or VPNs involved? Are you using NAT to get to and from the phones?

We’ve seen Polycom lose track of the “hangup” packets in the last, but IIRC, that was with a VLAN installed. The terminate packet didn’t get sent from the phone on the VLAN but was processed in the base LAN, and the packet was lost.

Using NAT. No VLANs or VPNs involved.
Port mapping, etc. looks consistent through the NAT.
Eventually the phone reconnects.
Using Sonicwall at the remote site – ALG is OFF and Consistent NAT is ON.

This is a NAT problem. Goung UNREACHABLE means the PBX didnt get replies to keepalives. It coming back eventually is the phone re-regisrering and opening fresh NAT holes

Thanks for the reply.
Yes I agree the phone stops replying to the keepalives (SIP OPTIONS) and that is why it goes Unreachable.
The problem I am trying to solve is why it stops responding.
I am trying to do some tracing at different points in the network to pinpoint the problem but that can be challenging.
I was putting this out there in case someone might have some valuable experience after seeing a similar issue. The one thing that I think is useful information is that I am seeing it happen after call tear-down.

What kind of router and how many phones + sidecars and/or +BLFs?

Sonicwall. 7 phones, no sidecars
Still trying to log at various network locations and catch it when it happens…its intermittent.
UDP timeout is set to 3600 so should not be timing out.
My current theory is the Sonicwall starts blocking for some reason but I haven’t caught anything relevant in logs yet.

For what it’s worth. I have had nothing but problems with Polycom phones and Sonicwalls. I have given up troubleshooting the issues as I could never get a consistent cause for the problem.

I’ve been using Polycom’s for years, they are not the issue. Sonicwall is the issue. I’ve had to deal with Sonicwalls screwing up SIP traffic from phones (doesn’t matter the brand) to simple SIP trunks on FreePBX/Asterisk behind the Sonicwall.

All Sonicwall defenders can say is “It works but it takes some tweaking and knowing where to tweak”.

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