Set CUCM to re-register all phones at least every 3 hours

[justin.e.thomas8.civ1]

Good day all,
I have a requirement to force all phones registered to my CUCM (11.5) to un-register and re-register to the call manager at a minimum of every 3 hours. I don't even know where to start on this one. Any help would be greatly appreciated.
Thanks in advance.

[Andrew Skelly]

Justin, out of curiosity what is the driving force behind requiring all phones to re-register every 3 hours?  Wondering if there is an alternate solution that may be more manageable.

[justin.e.thomas8.civ1]

Hello and thanks for your question. The driving force behind this is a requirement placed on the organization by a higher headquarters. I have as yet been able to get an exact answer for why the requirement was made or how exactly we would comply with it without interrupting service every 3 hours.

[tomahawkeer]

As Justin said, it is a requirement for a government entity. I have also, not found a solution for this.

[TONY SMITH]

You can configure a BAT job to reset phones, and to recur at intervals.  You can only select hourly, daily etc.  However I guess you could set eight jobs, each running daily but offset by 3 hours.

[jim-j]

I'm also curious as to why you'd want to do this, but wouldn't a simple bulk admin job scheduled to restart the phones every hour work?

[telephone guy]

I have the same problem, it is a DoD STIG requirement for 2020

[telephone guy]

There is also another one that The Voice Video Session Manager must require Voice Video peers (trunks) to re-register at least every hour.

[TONY SMITH]

I think it would be worth checking the exact wording of the legal requirement here.  The Cisco phones all have some form of keep alive, so if the requirement is for the components to check connectivity at no more than three hour intervals, they're doing that already.  Same with Options Ping on SIP trunks.

[andeporter]

I would consider bouncing the phones from the switch via PoE if you still haven't found a solution to this. Seems like you could write something to do a power inline never power inline auto on the switch ports.

[alexstouffer@gmail.com]

Justin, this requirement should met based on DHCP & networking settings. Think of it this way, if the devise looses IP it must re-register. So your DHCP timeout would dictate that it re-registers every time it updates the IP (even if it gets the same IP).  You shouldn't need to reboot the devises to make this happen.

So if you're running default settings, it happens in a much shorter time then 3 hours. I mean if you unplug it, how long does it take to show "unregistered",? The signalling communications happens about every 5 seconds.

[TONY SMITH]

Cisco phones don't re-register when they renew their IP addresses via DHCP, unless the renewal fails and they get a different IP.  We had a customer who for some reason set his DHCP lease to one hour, and his phones definitely weren't re-registering every 30 minutes.

[alexstouffer@gmail.com]

But what was the endpoint session traffic? Re-registration, is just validating what CUCM already knows.  If something changes (like IP) then it would update in CUCM. Maybe it's "registration light" but still performs the same function.
I'm referencing this as it pertains to Government requirements (STIG) which is a different beast.

[TONY SMITH]

 Best thing would be to Wireshark an individual phone and see exactly what it does during a DHCP refresh/renewal.   My understanding is that the phones try to renew when they're at 50% of the lease time.  

Another point maybe not mentioned, if you need to "un-register and re-register" at no more than three hour intervals, that means it's going to be happening during working hours, so unless you want to drop active calls it needs to be a non-disruptive mechanism that will wait until the phone is idle.