WIC 1DSU-T1 vs VWIC2-1MFT-T1/E1

Question:

I'm looking at a production router Catalyst 3560X  with a VWIC2-1MFT-T1/E1 module and neither side of the serial p2p connection has any clock rate configurations. Now I know with the VWIC2-1MFT-T1/E1 that everything is configured under the controller interface. However I'm seeing no clock rate command like with the WIC 1DSU. How does this work? Does that mean that there is a DSU/CSU at that location? I'm just used to seeing the WIC 1DSU-T1 more and haven't worked with the multiflex modules before.

Answer:

If you have a WIC-1DSU-T1, WIC-1DSU-T1-V2 or HWIC-1DSU-T1, you need to go under interface configuration and type service-module t1 clock source:

3845_2(config)#int serial 0/1/0

3845_2(config-if)#service-module t1 clock source ?

  internal  Use adapter internal clock

  line      Recover clock from line

You have 2 options here as you can see. Internal provides clocking and line receives clocking. In a back-to-back circuit, it is recommended to configure one end as "internal" while the other remains "line". If your provider is in the middle providing clocking for both ends, the "line" configuration is recommended but this depends on the circuit specifications. You can use the "show service-module" (do not forget clearing the counters to see the fresh statistics) command to know if there are clocking issues. Basically, you need to focus on the " Slip Secs" value. If it is increasing, it is recommended to check if clocking is properly configured. Sometimes you will need to get the provider involved to confirm the proper clocking configuration you should have.

On the other hand, if you have a VWICX-XMFT-T1/E1 you need to enter controller configuration and choose the proper clocking configuration. It basically works the same as in a WIC-1DSU-T1 and similar hardware.

3845_1(config)#controller t1 0/0/0

3845_1(config-controller)#clock source ?

  free-running  Free Running Clock

  internal      Internal Clock

  line          Recovered Clock

"The free-running keyword  specifies a free-running clock derived from the oscillator on the  motherboard, which is used only for testing and back-to-back  connections".

http://www.cisco.com/en/US/docs/ios/12_2/12_2z/12_2zj/feature/guide/gthwecan.html

To look for statistics use the "show controllers t1 X/X/X" command and avoid using any "loopback" command for it would affect the connection since it is used just for testing purposes. WS-C3560X-24T-L I hope this information helps and do not forget rating the useful posts.