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Ajay Wadhwani

Maximum number of extensions on UC560 telephone system


I have a client who is looking for a 135 user telephone system. I know that the Cisco documentation mentions support for up to 138 users but has anyone tried the telephone system with these many users?

Please do let me know.


Ajay Wadhwani                  

Scott Martin

While technically possible, I think you would be pushing the limits of the system, and not providing any headroom for your client's potential expansion. We usually like to allow at least 20% headroom.

You are looking at a UC560 + 13 x L-UC-PRO-8U= giving you 128 user licenses, 10 supplemental user licenses, so you are at the top end of the limit.

You may wish to look at the CUBE3000 ( which would be a better fit for that size client as it will support up to 300 extensions.



David Trad
Rising star

Hi Ajay,

The UC-560 is quite a beefed up unit and is quite capable of handling 138 Users (More if you remove the FXS licenses)... However there is a BIG "BUT" on this, and Scott has pointed out one of them.

When ever you max out a system you start to do tight rope walking without the balance bar, the system resources may be able to handle that many users, but what happens if you enable every single feature on the system? I can tell you You start to run into odd issues, such as random reboots, dropped packets on the voice and Phones also randomly rebooting... I suspect that this may not be 100% due to the hardware, maybe an IOS issue for this particular appliance (Yes they are not all exactly the same).

So my recommendation to you is consider the BE-3000 series, this unit is very very powerful, has great feature sets, and is expandable to a degree, the downside is that at my last inspection it had limited support for phones I.E it supported only the 6000 series (This I would hope has changed), and it is purely a SIP based appliance for the phones, and it accepts PRI or SIP trunking (I dont know about BRI).

In my opinion the BE-3000 is an evolutionary design from Cisco, whilst I argue their approach on it was not fully sound, they have continually worked to get it right which in my books makes it equal to or better than the UC-560, I also note that it is just as simple if not more simplier than the UC-500 series to setup and maintain, it is 100% all web GUI-On-System which is 100% my preferred method rather than a desktop GUI.

I hope I have given you an alternative to look at instead of confusing the issue



Cheers, David Trad. **When you rate a persons post, you are indicating a thank you or that it helped, but at the same time you are also helping to maintain the community spirit - You don't have to rate posts and you wont be looked down upon :) *
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