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New Member

WIC CSU\DSU T1 Configuration


I am configuring an internal CSU\DSU T1 WIC for the first time on a 2600, as I am used to configuring Serial int for external CSU\DSU. Are there any other configurations needed for this hardware to connect to home office using Frame-Relay. Any help is appreciated.


Re: WIC CSU\DSU T1 Configuration

Before configuring layer 2 (frame relay) and layer 3 on the interface, you will need to configure the layer 1(T1) characteristics. These must be set up to match the T1 delivered by your carrier:

service-module t1 framing (esf|sf)

service-module t1 linecode (b8zs|ami)

service-module t1 timeslots (enter the number of timeslots, if you are getting fractional T1 service from your carrier)

These commands will all be entered in the interface config mode for your serial interface. After this, set up frame relay and your layer 3 configuration just as you are used to doing on "normal" serial interfaces.



New Member

Re: WIC CSU\DSU T1 Configuration

Transitioning from 3825 to 3945 (OS is 15.0(1r)M13 c3900-universalk9-mz.SPA.151-4.m4).  Turning on FDL on the 3825 was easy but the same command on the 3945 doesn't work.  Any ideas?


Re: WIC CSU\DSU T1 Configuration

service-module t1 fdl both

This allows for the Lec to loop your CSU

Cisco Employee

Re: WIC CSU\DSU T1 Configuration

Here is the link which talks about configuring T1line with CSU/DSU integrated



New Member

Re: WIC CSU\DSU T1 Configuration

Serial Interface Troubleshooting:

Facility Data Link (FDL) is a 4-kbps channel provided by the Extended Superframe (ESF) T1 framing format. The FDL performs outside the payload capacity and allows a service provider to check error statistics on terminating equipment without intrusion. There are two ‘troubleshooting’ protocols for the FDL format; ATT and ANSI.

  • AT&T created and implemented the first ESF FDL protocol named after the defining Technical Reference, TR54016. The AT&T protocol uses a command/response arrangement with the Customer Installation (CI) such as an ESF CSU, Multiplexer or PBX. ANSI defines the ESF FDL protocol in their DS-1 specification, T1.403.
  • The ANSI protocol requires the CI to generate Performance Report Messages (PRMs) at one-second intervals. The advantage of ANSI T1.403 over AT&T TR54016 is the monitoring equipment in the network can be non-intrusive, increasing circuit reliability. TR54016 and ANSI T1.403 conform to ITU Q.921 and can coexist on the same 4Kb/s ESF FDL. AT&T supports equipment conforming to both TR54016 and ANSI T1.403. It is recommended that new CI support both TR54016 and ANSI T1.403.

ATT Troubleshooting on T1 for Costco can use either ANSI or ATT, but prefer ATT protocol. To insure that no matter which protocol that they use, it is best to set the outside payload capacity troubleshooting for both ANSI and ATT. Enabling this on the serial interface doesn’t compromise the bandwidth since this is a channel that is set aside for this purpose and if a protocol is not enabled then the bandwidth carved out is just not used at all.