Friday, December 23, 2011

How to use individual E1 channels for certain purposes on voice routers

Hi Guys

Quick voice update here, I have been doing a lot more voice work recently, which is good for me. Obviously as a CCIE in Voice I need to keep the voice stuff up :p, but recently I had been doing more routing and switching.

Anyway, I came across something that I have always heard about, but never actually understood how to do, and It never came up in my CCIE Voice studies, so i thought I would post it here for all of you

Let's go through two scenarios, let's say you have a customer who has a 30 channel E1, and says i must ALWAYS be able to dial this number, even if all the channels are busy, there should be 1 channel free for emergency calls (in australia, 000 is our emergency number)

Here is how you would do it:

first, create two trunk groups

trunk group ISDN_OUT

trunk group EMER_OUT

then go to your E1 card and specify the timeslots:

controller E1 0/0/0

pri-group timeslots 1-31

trunk-group EMER_OUT timeslots 31

trunk-group ISDN_OUT timeslots 1-30

!

Walla! You now have two trunk groups, each with a seperate amount of channels, then you would just have some dial-peers (roughly) configured like this:



dial-peer voice 100 pots

pref 1

destination-pattern 000

trunk-group EMER_OUT

!


Then a normal dial-peer for all other calls, the great thing about voice router dial-peer matching is that, if the above is busy (so someone is already on an emergency call to triple 0), the voice router wont give up, it will fall to the next available dialpeer shown below (even though it does not strictly match), so that means you always have the ability to dial 000 and have more than one call, but at LEAST one call to 000 will always get through


dial-peer voice 1002 pots

destination-pattern 0T

trunk-group ISDN_OUT

!

You could use this same trunkgroup concept to take a failed channel out of service (i think there is an easier way to do it though)

I hope this helps someone out there


3 comments:

  1. Out of curiosity is there a way to use half of the timeslots on a T1/E1 for data and the other half for voice? If so what would the config look like? Great post!

    ReplyDelete
  2. Hi Jerred,

    Jeepers!!!! Tough one, i don't actually know, let me look into it for you

    ReplyDelete
  3. This was really common back in the day. Commonly known as add/drop or drop/insert. Here's a config where we pull 1 t1 in, take 10 channels of voice into the router and then take the data channels (12-23) and actually pass them out to another t1 port 0/0/1 where it connects to a csu/dsu.
    controller T1 0/0/0
    cablelength long 0db
    pri-group timeslots 1-10,24
    tdm-group 22 timeslots 12-23
    controller T1 0/0/1
    clock source internal
    cablelength long 0db
    tdm-group 22 timeslots 12-23
    interface Serial0/0/0:23
    no ip address
    encapsulation hdlc
    isdn switch-type primary-5ess
    isdn incoming-voice voice
    no cdp enable
    connect t1-data T1 0/0/0 22 T1 0/0/1 22

    To do what Jerred asks where the data is terminated in the router as well, instead of using a tdm-group, you could configure controller 0/0/0 to be a ds0-group and pass data over it. Something like:
    controller T1 0/0/0
    cablelength long 0db
    pri-group timeslots 1-10,24
    ds0-group 22 timeslots 12-23

    interface Serial0/0/0:23
    ! Voice here!
    no ip address
    encapsulation hdlc
    isdn switch-type primary-5ess
    isdn incoming-voice voice
    no cdp enable

    interface s0/0/0:22
    ! Data here

    ReplyDelete