CME overlay ephone

[ciscoforum]

What's the difference between "Two Ephone-dns with One Number" and "overlay ephone"? They both can accept simutaneous calls and can use the same number.

[palves]

Here's the differnce. Actually, it's not really accurate to portray it that way.

The idea behind overlay ephone-dns is that if you have two DN's as follows...

ephone-dn 1

number 2001

ephone-dn 2

number 2002

ephone 1

button 1o1,2

ephone 2

button 1o1,2

With the following setup, both DN 1 and DN 2 are on both phones. This means that if the 1st call is answered by ephone1, and the user on ephone2 wants to make an outgoing call, the line doesn't appear as already being used (since it actually has both lines on that single line appearance).

So what you get is the ability to use the 2001 DN more than once (if someone's on the line on the other phone). It also doesn't appear as being in use, when it's actually in use on the other phone. WithOUT overlays, the line appears with an "X" on it (in use). Overlays also allow the ability to put many lines on a single line appearance.

Hope this helps.

PS. The CME admin guide goes into great detail about this. One of the few Cisco Admin guides that are actually very easy to use and understand.

Paul

[ciscoforum]

But according to that admin guide, the feature of"two ephone-dn with 1 number on two phpnes" provides the same function as overlay. Here is the two ephone-dn config:

ephone-dn 13

number 1003

no huntstop

ephone-dn 14

number 1003

preference 1

ephone 4

button 1:13

ephone 5

button 1:14

That's what confuse me.Thanks

[palves]

Overlay lines make it seem that you have more than one line on a single line appearance (really it's just 2 separate lines with 2 extensions that happen to be the same number, mapped to a single line appearance).

If using the same extension (with 2 overlay lines) and a call comes into that extension, both ip phones will ring, if you answer that call, and place another call to that DN, the other phone will ring and accept another incomming call. Only overlay lines allow the ability to share a single line appearance across multiple ip phones and handle more than one call at a time.

You could do a similar thing with 2 DN's that have the same extension number (but different ephone-dn's). If you apply these both to 2 different phones, you are correct, you would have the ability to handle 2 incomming calls. Having 2 line appearances with the same DN on each phone can confuse people. It's the way it's usually done in CallManager. Doing it with overlays is a little more practical and scalable.

Overlay DN's are most often compared to sharing a single DN across 2 different phones. In that scenario, only 1 call can be active at a time (an X appears on that line on all phones that share that DN if the line is in use).

Paul

[ciscoforum]

This make sense. I got one more question. As you said and I also tested both phone will ring when use overlay with same number, so what's the purpose to have preference ? I thought if I have preference I can make one phone ring if its preference is 0(the other is 1). But actually both phone still ring same time. If reading the doc, it indicates it should ring the phone with preference 0. Could you check this link and check the "Figure 9 Overlay Ephone-dn" Casehttp://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123newft/123t/123t_7/cme31sa/cme31ovr.htm. this case says it'll ring the phone with preference 0 first. But I test it didn't work this way. thanks