BLF Max Channels

I have a site that is remote to the PBX. I have never set up a whole site with side cars and BLF for every extension within the company.

The issue is, some phones randomly seem to lose connection to the PBX, and BLF appears to be what is freaking it out. I was wondering is there a maximum number of channels that BLF can use, and if so, is this a system-wide limitation or per extension limitation? If this is a system-wide limitation, is there a way to resolve this issue? Also, they have 3 other remote locations that have 2 phones each with their own side car as well as BLF turned on.

So, doing the math, we have 27 phones, that are checking 27 extensions constantly, which comes out to be 729 checks every time they reach out to the PBX for the state of each extension.

FreePBX 14.1
Asterisk 16.6.2
OS CentOS 7

Any help here will be greatly appreciated!!

There is no limitation with the PBX and mostly a phone issue. Most phones have ability of using around 45-60 BLF keys. I would check the phone manual or contact your supplier for information about the max BLF keys that phone.

I think we actually narrowed it down to being the VM the OS and firewall was hosted on. We moved it to a dedicated host and the issues seam to have went away!

Actually, there is (or at least always has been) a limitation on the number of BLFs Asterisk can support. It takes processor time to plow through the list. It seems to me that 60 BLF keys per phone will effect the performance of Asterisk as well as the phone. We’ve seen “FRACK” errors on systems with “too many” solicited BLF subscriptions.

Changing the BLF type (Solicited, Unsolicited, or Auto) from Auto to Unsolicited can help performance.

OK, we resolved the issue by exporting or VM template and loading it onto a server that is local to the phones. This cleared up the BLF issues, as it no longer runs over the internet to check the extensions for their status.

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