Centralise UCM in geographical location


I would like to know whether I can Centralise 1 UCM and have multiple UCM connected to this UCM in different location.

Take for example:
I have 3 UCMs, UCM A and B are set up at Location A and Location B respectively.
Then UCM C will be the central unit where UCM A and B will be connected to.

UCM A --------------(through internet)-------------UCM C-----------------(Through internet)----------UCM B
(Location A) (Location Central) (Location B)

UCM A and B only can calls within their network and to UCM C
UCM C can call to UCM A and B

if this can work, will there be any issues if we have like 20 UCM connect into 1 central UCM?

This is a large project we need to find out whether this can work or not.

Thanks in advance


Yes it is possible.
You will need careful planing first as we have no idea what features you want use.
Also you need estimate calls between UCM.


Hi Marcin,

Thanks for the reply,

But I just wondering how should I get this to work?

Do I need to use VPN or do I set:

UCM A and B outbound through SIP and call to UCM C Inbound - to call to the extension.

I only knows how to connect 2 UCMs together within the same network by using peer trunk.
Is the concept same?


All explained in that document.

Simply create interconnect (very easy to do).

As for 20, which UCM u plan use ? How many calls ?
Normally you can interconnect all with all :slight_smile:


I have done this, albeit each UCM can reach extensions on any other UCM, through site to site VPNs. I suggest the use of VPNs May increase security and reduce issues.

As you will see you can control who can call who via In and Out bound rules on each UCM.

Don’t forget LDAP sync.

Good luck.


Yeah, I successfully interconnect 2 UCM together locally using this document.
Just want to understand, if I want to interconnect multiple ucm together over the internet.
For the Peer Trunk, do I set the hostname as the DDNS of the other device?



Yes, use the FQDN associated by the DDNS service to each UCM for the trunks.


Thanks for the reply,

I’ve tried using DDNS as hostname on each UCM, couldn’t get it to work.
Not sure whether is it the setup that I have now.

Right now both devices are connected to the same router, both DDNS are point to the same public IP.
As for now I’m in my office environment, thus there is no way to test with different router and IP.
I am just trying to stimulate the connection going through DDNS, and not sure whether is this the right way.

Pointing them locally using their local IP works well.


Wait, what?
Why are both devices (UCMs?) connected to the same router?

Your first indicated - “I would like to know whether I can Centralise 1 UCM and have multiple UCM connected to this UCM in different location.”

This will not work unless you do some configs in both UCMs and the router.


It is because my boss give me the scenario of having a Centralize UCM, and I like to ask whether can it be done. (which is answered that it can be done)
And as I mentioned, I have no way to do this setup with different router and IP, thus trying to stimulate the connection going through different DDNS even though it is connected to the same router.


Well…having both FQDNs pointing to the same IP, unless the router is dual Wan and has 2 or more IPs, is problematic and really does not emulate what you are trying to achieve.

There is much more to the setup by trying to do it this way.


I see, guess i have to bring one of the grandstream to my home to test the setup.


You can change SIP port in UCM then you can simulate it somehow. Anyway it is pointless as you already have prof that it works. IP and rest is Network not UCM thing.


Off topic from the above setup,
I have a question, whether can I failover analog line from 1 UCM to another UCM.
For example, if both analog of UCM 6202 is down, it can failover to use the analog line on UCM 6510


Yes, in outband you set failover to other UCM.
BUT !!!
If all lines are busy(used) then it will also failover. Failover mean no free line to call.


Alright, I have manage to bring one of the grandstream home, but i have encountered some problems here.

Home - UCM 6202
Office - UCM 6510

For UCM 6202 I’ve tested in office for internal calling and calling through App and it’s working fine before bringing it home to interconnect both UCM together.

So the problem I faced right now is that, after I managed to link 2 UCM together by DDNS, when I made internal call on UCM 6202, calling into UCM 6510 extension. Both resulted in having no audio or video.

However, when calling from UCM6510 into UCM 6202 I could get audio and video.
When making internal call on UCM6510, i could also get audio and video

Port 5060 (TCP) and 10k-20k (UDP) are port forwarded on both routers.

UCM 6202 -----Home router------internet-------Office router------UCM 6510

What could have been wrong here, I’ve checked both UCMs settings, and both are similiar.



In that case you must set NAT.
Both ucm cannot respond as SDP show internal number to contact. (turn off NAT on trunk).
DDNS i hope is global and provider can also use it.


Hi, thanks for the reply,
I’ve already set this 2 settings before posting up for solution, I’ve yet to try disabling NAT on trunk.
This setting is for the calling between UCMs, what about the internal call with no audio video on UCM 6202 (Home)?. It worked when I tested it in the office, but couldn’t get it work at home.:thinking:


What about the port forwarding on your home router and the office router to allow packets to pass ?


Yes. Port forwarded port 5060(TCP) and 10k-20k (UDP), is it more than enough or is there any other port that I need to forward?