Hi if anyone else ever needs help connecting an Avaya IP Office phone system with Twilio Elastic SIP trunking, feel free to reach out to me, we got it to work after some trial and error and the connection seems very good. Will save us some good money.
The final piece to the puzzle for us had to do with the IP address that Twilio sends SIP invites from for incoming calls to the Avaya system. To get this to work in the Avaya we had to set up 4 SIP "Lines" pointing to 4 different "ITSP IP Address" values and 4 "Incoming Call Routes" per DID because Twilio sends from 4 different domestic IP addresses. I did read some documentation about being able to leave the ITSP IP Address blank (0.0.0.0) since we do have the "ITSP Domain Name" populated but that does not seem to work in our situation.
In researching this on the Internet I surprisingly did not find much evidence of Avaya customers ever having to deal with this issue (with or without Twilio), however I did find some examples of some other PBX systems having this issue with connecting to Twilio but those systems seemed equipped to configure multiple IP addresses for a single line.
Thus my question - do any Avaya customers have a suggestion for an alternate configuration to make this work? Anything we could do on our firewall? Twilio does not support sending SIP Invites from a single IP address or via a proxy server address. Fortunately we only have about 10 DID's so this won't be that hard to setup and maintain.
Credit goes to zakabog at the Avaya support forum for answering this, who said:
"Setup the 4 different SIP lines but give the URIs the same incoming group ID, that'll let you use one incoming call route for each DID."
My reply: "That sounds like a very good idea. I will try that and report back. You are referencing the "SIP URI" tab right that we'd point all 4 of them to line 19 even though we have setup a line 19, 21, 23 and 25, right?"
His reply:
"Exactly, there is the line number and then there's the incoming and outgoing ID, and those numbers don't need to match. So you can have everything share the same incoming or outgoing group ID, it helps keep the ARS and incoming call routes less cluttered."
And my final reply (it worked!):
"Yes that works like a charm. Much better, I don't mind setting up 4 SIP lines but wasn't thrilled about dup'ing the other stuff. Thank you thank you."
I received following question later on the Avaya forum:
"I do need help trying to get this up and running. The main issue is that we can not resolve the ITSP Domain Address field in the Line -> SIP Line -> "ITSP Domain Name" with {our-domain}.pstn.twilio.com
It would be REALLY interesting, step by step, how you would go about getting Twilio to work with 1 SIP trunk on Avaya Office."
My reply:
"Yes, this was my issue too. The way we have it working is by creating 4 SIP lines for each of the 4 Twilio domestic IP addresses (SIP Line tab), 54.172.60.0 through 54.172.60.3. And then using zakabog's suggestion we use only one of these line numbers on the "SIP URI" tab. This allows to only have to create 1 set of "Incoming Call Routes" pointing to that same "Line Group ID" as is shown for the "Incoming Group" and "Outgoing Group" on the "SIP URI" tab. Please note that these call routes will require the "+1" for the "Incoming Number", assuming these are US DID's. Feel free to send me a phone number or email address and I'd be glad to arrange a discussion with you or show you my screen."