We are in the process of reviewing our AT&T SIP IP Flex circuits due to the time that it's taking them to complete phone number ports and any other changes. Unfortunately, this is taking months, not weeks.
I have reviewed a SIP provider, NexVortex, and have been impressed with the one site that we've already stood up with them. The amount of time to be assigned a phone number and even the porting of numbers has been very quick, days not weeks or months.
For our offsite locations, we currently are using a mix of some locations using AT&T IP flex so that the location would have their phone numbers exist in their building and some locations have their phone numbers that exist back on our corporate SIP IP Flex account.
Each works just fine, but the location based IP flex circuits are 1) expensive and 2) requires a cube router to be installed at each location.
We are considering moving to NexVortex's mSIP (managed SIP) option for our corporate site and all branches. We would install two new 4431 routers, one at our Corporate Office, and one at our DR site. These would be connected over DIA circuits with a vendor that they peer with so that we can ensure QoS and monitoring.
While this on paper sounds like a great deal and gives us the flexibility and agility that we need, I'm just asking if someone could point out any issues that we might encounter.
For reference, our CUCM cluster has one CUCM server at our Corporate Office and one at our DR site.
Sorry, the hope is to get away from standing up individual cubes at each offsite location. This would cut down on us installing CUBE routers at the 40+ offsite locations. The 4k routers would be our corporate and DR cube routers to house all of the SIP trunks on.
Today each of the off-sites are quite small with just a single Meraki security appliance which is using the auto VPN back to our DR site and only has 5 - 10 users in each site.
Each of the sites today have 8845 phones that are registered over the IPSEC tunnel back to our CUCM cluster.
The one issue I can see is that we would lose the ability for 7 digit dialing. Employees would be required to dial 10 digit everywhere since I wouldn't know what their local area code is since it's all coming off the corporate cube.
From what I am reading it appears you want to centralize your CUBE deployment.
Ie Have two CUBEs rather than having CUBEs per location which sounds to me like a PRI deployment. I dont see any issue and here are a few considerations
1. WAN. The connectivity from each location to the DR/HQ is critical. In your current deployment, your media doesnt traverse the WAN. It is local to each site. Calls coming from the phone have there medial terminated on their local CUBE. When you migrate, all your media for these remote sites will traverse the WAN. So you need to consider that. If you are using IPSEC tunnel back to HQ/DR sites then plan accordingly on how you will implement QoS on this. This setup is not often the best to run voice media on..so plan well here
2. Dial Plan. Your dial plan doesnt need to change. Users can maintain their dialling habit, you just need to reconfigure your CUCM dial plan to handle this.
3. Emergency services. Ensure your ITSP can identify the location of each of your callers based on their CLI.
4. Be aware that you cant have box-to-box ( CUBE-HA) cube with your current proposed setup. CUBE HA requires that both CUBEs live on the same VLAN.
Depploy 2 cubes; one in the head office and one in DR, port all relevant DID ranges onto the SIP service that will terminate on your CUBEs, then have dialpeers to your cubes, pointing tio your cluster(s).