Several extensions showing UNKNOWN status in CHAN_SIP PEERS

Using FreePBX 13.0.26,
I have about 5 particular extensions that are showing up as UNKNOWN in the show sip peers report. These users are complain that they are missing calls. Sometimes I can call them and they go straight to voicemail. If i reboot the device they register and show up in the peers report but then go unknown and appear to bounce back and forth. It’s only this handful of extensions. A mix of models, using the same template and firmware as other devices in our network but these 5 extensions are the only ones doing it. reset the devices to factory defaults and reload their configs. did a fresh config and even built a new template.
2 devices are Grandstream GXP-2100’s
2 devices are Grandstream GXP-1450’s
1 device is a Grandstream GXV-3611HD

My guess is you need to fiddle with the firewall settings at the remote site(s) where the extensions show up UNKNOWN.

If the device registers on reboot and then disappears from the network you’ll need to disable SIP ALG on the REMOTE routers. You may also have to disable the SPI firewall and turn off “block anonymous Internet requests”. Lastly google the specific router model number to check if they are compatible with SIP.

If you have control over the routers you can also open up the ports in the firewall. TCP/UDP 5060 and UDP 10000-20000

Thanks for the suggestions. I forgot to mention that all my extension are on the same LAN as the server. There isn’t any particular switch that is common to these 5 devices. The trouble began right after upgrading from 12 to 13

On Grandstream each ATA must have it’s own SIP port if they are on the same LAN. 5060, 5061, 5062, etc… You can also try the setting “use random SIP port”.