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Blue

DID's for analog trunks with SRST

Hopefully a simple TDM question.

If I have an office of 25 people. I want to run SRST at my office. I do not want a PRI. If I have 12 analog trunks can I have 30 DID's? Or do I need an analog trunk for each DID. I was hoping I could tell the carrier my DID's and they route the calls to the 12 analog trunks. Hopefully I do not have to have a PRI.

9 REPLIES
New Member

Re: DID's for analog trunks with SRST

No, you don't need a PRI, but you will need analog DID lines to be able to route inbound DID calls to their corresponding extensions. You can put hundreds of DIDs on a single analog line, (but that wouldn't be very efficient.) For an office of 25, four analog DID lines (these are inbound only lines - see below) and four standard analog lines should be plenty.

You will also need Analog DID FXS VICs, as FXO modules will not accomodate analog DIDs. The caveat is that analog DID equipment supports inbound only, so you will need standard analog lines (and FXO modules) for outbound calling as well.

Blue

Re: DID's for analog trunks with SRST

Really appreciate the reply.....Just so I fully understand this. You can't place these DID's on a standard analog trunk....you are saying that you can't use the standard analog trunks for inbound and outbound calls. These DID lines are the only thing you can use for incoming calls on regular POTs lines? So physically these DID lines from the CO will connect to a regular FXS card or a special DID FXS card? Lastly, are you aware if the NM-HDA supports and DID VIC's?

Bronze

Re: DID's for analog trunks with SRST

I ran into the same issue. You have to get special 2DID voice cards to use DID with analog. Since you can't make outgoing calls you will need additional anaglog interfaces. This poses a problem, depending on your gateway. You will be able to put ONLY 4 DID lines per NM, and the cost is not cheap. Then in order to have additional analog lines you will need another NM slot. This meant to me that I would need a 3725, or 3640, something with 2 NM slots. Or I would need 2 routers! The cost of the larger router or the additional, and the DID cards was more than a PRI card and a PRI. Do your own estimation, but be prepared to spend some coin! I am using a 2651xm with a PRI card and CSU over VPN, and everything works great! Loosing a couple of packets here and there is okay, but loosing voice calls will get you into trouble fast! I would not use any shortcuts here, because your ass is on the line!

Geoff

Blue

Re: DID's for analog trunks with SRST

Also, don't Iose caller id with those DID lines.

Bronze

Re: DID's for analog trunks with SRST

Not quite sure what you mean. If you go PRI you can do "call by call" for rollover and your DID lines will be DOD also. You can call out and in on the same line. By the way I am using Informacast, and it is a great product! Good job!

Geoff

Blue

Re: DID's for analog trunks with SRST

Thanks, yeah it a great product. Our Developers do an excellent job. I am talking about losing the caller id if I do not go with the PRI, I am not sure if the analog DID lines support caller id. This client already has a 3660 and a bunch of NV-2Vs and VIC-2-FXO-M1's from other branches of there company that moved to PRI's. This office is only 25 users strong and there Network Admin can get the pots lines for $20 per month.

Blue

Re: DID's for analog trunks with SRST

Can I get caller id on DID lines. What good do theses DID lines do me if I can't get caller id. Is there any way to get a block of DID's on an analog line so I could have four analog trunks that could do inbound and outbound on the same lines?

Bronze

Re: DID's for analog trunks with SRST

Yes you can do CLID on the DID lines. I agree it would be useless. I my speaking with the Telco they told me that you can't dial out of a DID line. It is a special DID trunk that does not have dial tone. Sorry, I wish that I could tell you yes, I was blind sided by this also. Also you will need the 2DID cards for their 3660. Here is an article that will give you all you need:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t2/dt_did.htm

Geoff

New Member

Re: DID's for analog trunks with SRST

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