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PABX and UC540, remote user and FXO connection to PABX

Dear experts!

We are planning to deploy a UC540 system along with our current PABX.

PSTN --> PABX (with anlog phones) --> UC540 --> IP Phones

We have some questions that need your help to clarify before deciding to deploy it.

1. Are there any problems if I have 8 IP phones at the main site and 10 other IP phones at a remote site which has been connected to main site using VPN ( and of course in different subnet). I ask this question because it is stated in the datasheet that there are only 5 "Users per teleworker site" license with UC540.

2. As each IP phone need a unique "ext number" as any current analog phones. I plan to to connect from FXO port of UC540 to ext of current PABX. because the maximum FXO port on UC540 is 8, is there any solution to have 20 connection from "PABX ext" to " Cisco UC? Will a FXO SIP gateway solution work or not

Tks so much for any help !

4 Replies 4

paolo bevilacqua
Hall of Fame
Hall of Fame

1. That is fine and not a problem.

2 You can do that however doing PBX integration via FXS/FXO produces poor results, like that when legacy PBX dials to ro Cisco they hace to go trought a 2nd dialtone to reach the final extension. Plus assorted other annoyances.

So the best approach is that you show and sell the complete system to the customer, and avoid integration at all. Also make sure that you engage a reputable consultant ot UC certfied Cisco partner for the job, otherwise you risk many hours of frustration trying to do yourself.


The post has been moved to the correct area.

Cindy Toy
Cisco Small Business Community Manager
for Cisco Small Business Products
twitter: CiscoSBsupport

Regards, Cindy If my response answered your question, please mark the response as answered. Thank you!

Dear Paolo,

Tks for your answer. Please help me with some more questions!

1. As you said that It will be fine if I have 10 users at a remote site. Can you please explain what  does "5 Users per teleworker site" limitation mean.

2. To clarify my planning, I intend to connect UC with analog PABX using E1 connection. For integrating IP phone and analog extension, I plan to use "Call forward" feature.

a. For Analog ext to IP ext calls, For example, if analog ext 101 is moved to UC system. I will set up call foward on analog PABX to forward all call to analog extention 101 through E1 trunk to IP extention 101. Will this make the integration seems to be transparent or not?

b. IP ext to Analog ext calls. The same rule apply. I well create IP ext coressponding to analog ext on analog PABX, then forward all call to the corressponding analog ext

I'm not sure  it will work as I think or not. Please help me.

Tks so much.

Hope to get help from you and support team soon

1. there are no actual limitations to number of teleworkers.

2. what you want to do is not easy, if you never did advanced telephony integrastion before, you will meet a lot of issues.

That is why you should seek help from a reputable consultant or UC certified cisco partner. And even this way, it will not be easy.