BLF on Mitel 5224 phones breaks incoming calls -- busy signal

I have some Mitel 5224 phones, and I’m trying to get BLF working properly.

The phones initially had firmware V7 on them, but I couldn’t find any kind of BLF options in the configuration pages… when I upgraded to V8, I had some BLF options.

Anyway, BLF works to a limited extent when I program a key to be a Speed Dial+BLF key, and enter in the extension number to be followed on BLF. I also have to add this extension number to “BLF User Group List” under “User List Config” in order for it to work, but it does indeed work…

Anyway, this all works fine except when I add more than two or three extensions in the “BLF User Group List,” that phone will stop receiving calls altogether after some unknown amount of time – possibly 10 minutes, 30, an hour, or so. The phone can still make calls, and BLF still works on that phone, but any call made to that phone goes to the “busy” voice mail. If I narrow the number of extension in the “BLF User Group List” field down to one or two, then all is well again.

So I’m trying to figure out what gives. The firmware version is Would be happy to provide any additional info I can!

Don’t know if this will help, but here’s a snippet from the Asterisk CLI. Ext 211 is the caller, and Ext 207 is the problem Mitel 5224. is the IP of Ext 207.

== Extension Changed 207[ext-local] new state Ringing for Notify User 207 (queued)
– Called SIP/207
– Connected line update to SIP/211-00000192 prevented.
– Got SIP response 486 “Busy Here” back from
– SIP/207-00000195 is busy
== Extension Changed 207[ext-local] new state Idle for Notify User 207 (queued )
== Everyone is busy/congested at this time (1:1/0/0)

Another update. I installed FreePBX 2.10 on a VMWare server and configured a couple of the Mitels to work with that. So far, BLF has been working well with six “followed” extensions, and I haven’t once gotten the busy signal.

So I’m not sure what to think… on 2.9, the Mitels have problems with BLF, yet my Grandstreams work fine. But on 2.10, the Mitels work fine.

Must be some configuration thing between 2.9 and the Mitels, but I wish I knew where else to look to figure out why the Mitels are reporting as busy!

I don’t think it is a FreePBX issue as much as an Asterisk issue.

Was the Asterisk version the same between the two?

That’s a good point.

The old (problem) server is running, and the new 2.10 server is running

Would you have any suggestions on how else I could diagnose the issue? Or would an update-source on the old machine be a good idea, to bring the Asterisk version up to date with the new one?

I went ahead and updated to FreePBX and Asterisk, and surprisingly (to me, anyway) the problem still persists!

At this point, I’m guessing a clean install might fix things, but I would hate to have to go that route. I wonder what could be messed up in the current installation that could cause this.

I have an customer that was migrated from the Mitel system so it still uses the same 50 or so Mitel phones in SIP mode, they vary from the 52xx and 53xx models, i have found out that the 52xx has a very low CPU power, and i have had problems with the same model 5224 before, when i added 8 BLF keys to the phone, the phone sudenly started denying calls (Busy Here), after searching it seems to happen only when the monitored extions where in high call trafic. (which was the first 45min of every day)
When i lowered this to 6 Keys is kept on working, the same i had with an 5324 model, on this the key limit was around 10.

I seems that the Mitel phones are not capable of handeling the amount of Status/Subscribe trafic that we would like them to have, the number of BLF Keys depends on the call trafic on the monitored Extension so YMMV.

With above said, i hope i shed some light into you problem.


Using Mitel FW 7.04

That seems to correlate with what I’m experiencing. If I add more than seven or eight BLF lines, I get the busy signal.

Thanks for chiming in!

Asterisk doesn’t support BLF list. You have to subscribe to the hint.