I do have a couple of peered systems but, stopped using BLF’s back in 15.xx because it’s just crap. I’d tell you the problems I’ve had but I’d just get mad and stressed again. Perhaps @drostoker has some comments. I know he’s got a couple peered systems too.
Seriously, my heart is pounding now just thinking about the crap I went through. So. It all started on a lovely winters evening. Then it all became crap, utter garbage. It was one of those one way updates. New database or something.
I performed a standard upgrade on two interconnected systems after waiting a couple of weeks and checking feedback on the forum. After the update, all at once, phones where no longer programmed correctly, something changed in the peered trunk (I don’t recall) and the BLF’s stopped working. Perhaps I shouldn’t have but, I did the upgrades remotely.
From my perspective, everything looked like it had gone well. Other systems to update, moving on.
First call came in at 7:00 am, after staying up late updating systems, this was early for me and I take ownership that I should have controlled the whole process better. I was tired.
Regardless. I spent all day on the phone with GS, with two or three reps. We worked out the trunks right away so, at least calls were routing between the two offices.
I should also say, I’d only sold a couple of system as this time and was very inexperienced.
Still had to figure out why the phone programing was borked and the BLF’s were not working.
Finally figured out that the pcodes I programmed where moved down by 1 in zero config. So, my first pcode was correct. Somehow my second pcode was blank. my third pcode had the second pcode value and so on.
Fix the template and push to phone. They are now working without BLF.
I know I’m rushing through this but, with packet captures and screen sharing with GS, it was end of day for them. They told me to factory reset both systems and rebuild by hand and that they were closing the ticket.
Factory resetting them at this point was no longer an option as the two offices had closed. I worked on the systems all through the next night and part of the next day.
Call GS back and they wouldn’t speak to me until the systems had been factory reset.
So, the customers limped along for a couple days until the weekend when I went in, armed with a bunch of screenshots and what not, and factory reset the two systems. Everything worked except the BLF’s. GS said that using the new backup files, they were able to reproduce the problem and it should be fixed in the next firmware update. a couple of months later, the customer insisted I buy back all the side cars which were basically useless now, which I did. Managed to sell them on ebay as used for more that I paid so, not a total loss.
That was almost the last time I dealt with GS. But I know from my days as tech support that sometimes the company is not represented by the front end staff. So I chatted with @lstutesman @drostoker and others and was encouraged.
To date, I have not attempted to interconnect UCM’s as I’ve become convinced it’s not stable. Which is why I referred you to @drostoker who’s had better experience and probably does not share my emotion based bias.
My largest system, which required BLF’s to work stable at 14 sites across North America, is hosted in an onsite data center with fiber and a solid wisp backup providing service. Great UPS that was preexisting for other IT infrastructure. Two 6510’s with HA, that system works great. I’d much rather focus on one reliable location and connect the other offices in to the main system. But I digress.
Also, no other systems I updated that evening had issues. Just the interconnected one.