Connect two router serial interface

[wfqk]

Hi As we know, when we want to connect two router back to back together, we need to configure clock rate on DCE side. But when I did so, both routers all have error message as below. Anyone have any idea for this ? Thank you

Router2(config-if)#clock rate 56000
%Error: This command applies only to DCE interfaces

Router1(config-if)#clock rate 56000
%Error: This command applies only to DCE interfaces

[syed kazim abbas]

Hi,

check the serial interface to find out whether it is DCE or DTE with this command
show controllers serial 0/1 then give the clock rate command. Can you tell us your router model and ios version?

Regards,

Kazim

[wfqk]

Hi Kazim, Thank you for your reply. The two routers are 2811. and please see its show controller and show ver in attachment. My further question is how the router decide which one is DTC or DCE since the two routers are the same type in this environment ? 

[syed kazim abbas · Accepted solution]

Hi,

you are using FT1 CSU/DSU module, so you need these commands instead clock rate under "Interface serial 0/0/0".

one side:service-module t1 clock source internal   

other side: service-module t1 clock source line

Also, make sure you have a T1 cross-over cable between the routers.

http://www.cisco.com/c/en/us/support/docs/routers/2500-series-routers/10265-52.html

hope it will helpful then don't forget to rate the post.

kazim

[wfqk]

Thank you so much! All are working well after adding the command you mentioned

[syed kazim abbas]

Welcome any time!