This week we had a strange customer issue. We were migrating a customer from one building to another, one Windows Active Domain to another, and an old antiquated phone system to Microsoft Lync – all on the same weekend. I know, right? Anyway…
The phone system cutover – including the Sonus SBC 1000 running firmware version 3.2 – went well. We migrated their PRI to the Sonus successfully and their test SIP trunk to our friends at Intelepeer was actively working.
On day two we ported over a couple hundred DIDs from their PRI vendor to Intelepeer. We actually physically moved this Sonus SBC 1000 from the old building (where the PRI existed) to the new building (which is Intelepeer SIP only) at the same time.
Here’s the problem – when the Sonus SBC came back online – inbound calls from our SIP trunk failed. Every single one of them.
We went about troubleshooting with our phone system (Lync) but the problem happened at the Sonus SBC before the call ever made it to Lync. The error Intelepeer got was SIP 405.
Sure enough – using the Sonus SBC LX (syslog) tool – we saw the same error in the SIP tree:
The call invite comes in and immediately a SIP 405 “Method Not Allowed” is shipped back to the SIP Carrier.
What could this be? I quadruple checked all my Sonus configurations. It was right. I quadruple checked all my Lync configurations (which is irrelevant since the call fails immediately at the Sonus) because I don’t want to leave any stone unturned.
I called Sonus TAC and opened a case. Sure enough, this is a known bug.
I was running Sonus SBC firmware version 3.2.0 build 315. From time to time, this bug means that a SIP INVITE comes into the SBC, but there are no destination signaling groups (downstream destinations) available for the call, so it ships back the SIP 405 “Method Not Allowed” code. It only seems to happen on power outage. And, since I had lost power to physically move the SBC, the bug hit. It made sense.
My TAC engineer Tracy was awesome. We chatted about the issue. I uploaded my LX logs and he was happy because I called with full information of the issue. He researched and came back with the bug report. I pulled down the latest firmware – version 3.2.1 build 321 – implemented it, and the problem went away immediately.
All this to say – we hope these notes from the field help someone. I couldn’t find a lot of useful information related to SIP 405 and Sonus on “the Googles” so I’m hoping this helps the next guy. Be sure to check your firmware: friendly advice from Uncle Daryl.