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E1 Clocking Back to Back 3925 Routers.

Just to get this clear as having issues with a E1 link with CRC's at one.

Router A

Network-Clock-Participate WIC 1

Controller E1 0/1/0

clock source internal

Router B

No Network- Clock Participate WIC 1

Controller E1 0/1/0

clock source line

Telco kit is unframed and passes clocking

Should router B have clock participate for WIC 1?

We currently have controllers set as UNFRAMED but guess we can set to NO-CRC4 both ends and telco will pass this.

Any thoughts appreciated.

  • WAN Routing and Switching

E1 Clocking Back to Back 3925 Routers.


Is Telco providing already the clocking signal? In that case, both sides should be configured for Clock source line.

If Telco is not providing a clocking signal, then your configuration is correct. try to add network-clock-participate and network-clock-select on both sides.

If there are still CRC's, you can connect a physical loopback interface on one E1, do a ping test and verify that there are no CRCs. After that you can verify the other side.

You can use this guide as reference:

Hope this helps