Part five on SIP will be rewritten; as some steps are missing.

Foreign Exchange Station or what the hell is FXS?

FXS is basically is what is in the landline world where the telephone line comes into a home or business. When things went to digital in the 1990s, not every phone system could take straight up ISDN, T1, DS1, etc. so a Customer Premise Equipment would be installed with basically an analog telephony dropdown. Adtran was  very successful in downconversion technology to tie a Partner key system into a large scale T1 line.

Then the advent of IP came along and tying older phone systems with native IP connections was very popular. In short, FXS acts as the Foreign Exchange Subscriber, that was traditionally foreign to the home central office of the customer.

In a Cisco environment, it can be used for multiple reasons. For today’s notes, it’s to extend analog telephones acting as extensions.

Wait, what’s the difference between an FXS and an Analog Telephone Adaptor?

An ATA is a separate device, that’s intended for things like fax machines, and some instances of analog telephones. Unlike Nortel and Avaya and even Mitel where it’s a box that goes embedded with a phone, the VOIP world likes to make little Netgear-like boxes instead. An ATA can have points of failure, and you’re not limited to ~ 300 feet of wiring. If say the network goes down (and it can!), you can have hard line failover, much like in your hybrid digital telephony setup. Unless something is wrong with the router, tricks to provide failover is very easy.

Again FXS can be used to tie analog trunk PBX systems or act as the ATA for a software based system like an Asterisk, this is intended for a Call Manager Express setup

To Start Dialing

Logged in and in configuration mode, type in voice-card 0/0 (in this example, first “o” is the gateway, “0” is the furthest right hand card on a Cisco 2801)

type on no shutdown

Then type exit

Now you need to type some more commands

First go to voice-port 0/0/0 (that’s Gateway 0, slot 0, port 0)

station-id name Dining Room (or another name or location you prefer)

station-id number 201 (or another number preferable, but you could leave this empty, but if you don’t hear it ring, you’ll know it was you!)

caller-id enable (this allows a Caller ID analog phone to give information from the caller, whether it’s a SIP call, SCCP call or even outside – Where Available, lol)

If you still struggle with Dial-Peers, it’s basically a dialing string or rule for anything other than Skinny phones. SIP is even foreign, and you have to create dial-peers for those stations too. Analogs do not talk in IP. When adding an ephone-dn or ephone; IOS already does that for you if you noticed. And you can tweak it if you so wanted to.

I used this approach dial-peer voice 1201 pots  in config mode

I told IOS, to have a destination-pattern 207

Port 0/0/0 – because that’s the port I put the station-id number on

Forward-digits all basically will dial the number after the person picks up, so if you want them to hear numbers dialing, than I’d leave it blank

The dial-peer is required if you have VOIP extensions whether it’s SIP or Skinny. The FXS slots when not in shutdown can make any calls against the dialing plans and dial-peers it knows, but it needs explicit instructions the other way around.

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