What a week, today is a bank holiday and I should be enjoying this rare treat but unfortunatly I’m spending it trying to jump start all manner of connections back in to life.

Anyway my headache of the week has been trying to decipher the differences between a channalized and unchannalized E1 service… not as easy (or as documented) as you might think!

E1 (Unchannelised).

A unchannelised E1 is exactly that, an E1 line but with no channels present on it. Usually an E1 is presented with 31 channels, this is not.

A unchannelised E1 is also known as an unstructured E1, clear channel, 2Mbit E1, full E1 etc… you get the idea! To support this service on our friendly Cisco 3845 (and indeed any of the other ISR range) you’ll need a VWIC-1MFT-G703. Note the G.703 bit on the end, required for unchannelised E1 support! Also note that on this circuit you will need to provide the clocking, clock from your router on one end and then from the line at the other.

To configure this on a Cisco router use the following:

! Firstly tell the router its an E1 card
! and then select the clock from it to stop skew issues.
!
card type E1 0
network-clock-participate wic 1
network-clock-select 1 E1 0/1/0
!
! Create an unframed channel group, this will use the full 2Mbit
!
controller E1 0/1/0
channel-group 0 unframed
!
! Issuing the above will create a serial interface
!
Serial0/1/0:0
ip address 10.0.0.1 255.255.255.0
!

Job done, you will have a 2Mbit unchannalized E1 service.

Channelised E1

Also known as structured E1, 1984k. This service will not work with the G703 card. For this you can use any voice/wan interface that supports E1. Another feature of this circuit is that the clock will come from the network at both ends.

To configure this on a Cisco router:

! Firstly tell the router its an E1 card
! and then select the clock from it to stop skew issues.
!
card type E1 0
network-clock-participate wic 1
network-clock-select 1 E1 0/1/0
!
! Create a channel group using all timeslots, this will use only 1984k of the channel.
!
controller E1 0/1/0
channel-group 0 timeslots 1-31
!
! Issuing the above will create a serial interface
!
Serial0/1/0:0
ip address 10.0.0.1 255.255.255.0
!

Note the subtle difference with the controller command. This will create a 1984k channelised E1 service.

Right I’m glad thats cleared up! Make sure when your ordering your E1 link your very clear on how you want your circuit delivered.

Normal service should resume this week…