Removing Carrier Initiated Loop on Service Modules and Serial with External CSU/DSU

[Daniel Mckibbin]

Hey Guys,

I know with T1/E1 controller based modules you can issue a  no loopback  under the controller and remove a carrier initiated loop. How would you do this on a service module without screwing with it's ability to accept remote loopback? How would a loop be removed on a serial interface with an external CSU/DSU?

Additionally I have a few more questions. The Serial interfaces and channels created from configuring a service module or T1 are logical interfaces correct? The serial interface itself does not exist, it's just the T1? The only case that the serial interface is physical is when it is like a WIC1T card or similar where it connects to an external CSU/DSU. Is this correct?

Thanks,

Dan

[rstanisl]

HI Dan,

I believe you are talking about a VWIC-1DUS-T1 card when you ask about the loopback commands.

You cannot remove a telco initated loopback from the router. You can do a loopback using th service-module t1 loopback commad on the interfac.

Loopbacks

Network line loopback - user initiated Recessed push button for network line loopback; toggle on/off Network line loopback - Telco initiated Network payload loopback Local DTE loopback Remote line and payload loopback (codes: V.541 loop up, and loop down)

Interface serial 0/0
service-module t1 clock source internal
service-module t1 timeslots 1-24 speed 64                 
service-module t1 framing esf
service-module t1 linecode b8zs
ip address 10.1.1.1 255.255.255.0

You can use the service-module command to change or do a loopback command on this card.
show service-module serial 0/0 will show you the stat for this card.

http://www.cisco.com/en/US/customer/products/hw/modules/ps3129/products_tech_note09186a00800b1501.shtml

To answer your other questiosn on the VWIC-1MFT-T1 cards that we us for t1 connections the t1 shows up as controllers. You have to configure a channel-group on the controller to createa a serial interface.

card type t1 0

controller T1 1/0

  framing esf

  linecode b8zs

  channel-group 0 timeslots 1-24

!

interface Serial 1/0:0

  no ip address

http://www.cisco.com/en/US/docs/routers/access/1700/software/feature/guide/t1e11700.html

Hope this helps

Raymond

[Daniel Mckibbin]

Raymond,

Thanks for the info. On a T1 controller (no services mod) that was being tested by a carrier. It was down/down after the test, showing looped by remote. The Carrier was showing it up and clean of errors. I hopped under the controller and issued no loopback and it came up. How do you explain this?

I always had a feeling that serial interfaces related to T1 cards were virtual and created under the controller configuration. I've just been so used to physical serial interfaces in my lab. I need to get a few T1 cards to practice.

Say I wanted to split the T1 into two channels would the config be similar to this?

card type t1 0

#

controller T1 1/0

#

  framing esf

#

  linecode b8zs

#

  channel-group 0 timeslots 1-12
  channel-group 1 timeslots 13-24

#

!

#

interface Serial 1/0:0
interface Serial 1/0:1






I know with a PRI you use pri-group instead of channel-group. Does there have to be a statement for each 
of the 24 channels on a T1?

[rstanisl · Accepted solution]

HI,

Looks like you had the old wic-t1 cards not the vwic-1duc-t1 card as I thought you had.

On the old wic-t1 card you can do a no loopback. That option was there, but on the new cards it is not.

You config is correct if you want to split the channels and create two serial links.

http://www.cisco.com/en/US/docs/routers/access/1700/software/feature/guide/t1e11700.html

The URL above has samples.

Unlike the PRI we do not have to have a statement for each channel on the serial t1.

Hope the info helped.

Thank you

Raymond