Hello Andy,
the clock rate command provides the OSI Layer1 clock that will be used to sample user data.
One side provides the clock the other side takes it from line.
The clock rate command has to be given on the DCE side of the cable.
To check what cable is sensed on the router interface use
sh controller serx/y
it should provide this info.
A T1 is defined as:
24 DSO channel + 8kbps control channel
1 DSO = 64000
so clock rate can use
int ser0/0
clock rate 1536000
or
clock rate 1548000
but you could use also 1500000 if IOS allows it.
Actually, according to IOS command reference
Desired clock rate, in bits per second (bps): 1200, 2400, 4800, 9600, 19200, 38400, 56000, 64000, 72000, 125000, 148000, 250000, 500000, 800000, 1000000, 1300000, 2000000, 4000000, or 8000000.
For some synchronous serial port adapters a nonstandard clock rate can be used. Refer to the hardware documentation for specific supported Lvalues. You can enter any value from 300 to 8000000 bps. The clock rate you enter is rounded (adjusted), if necessary, to the nearest value that your hardware can support except for the following standard rates: 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 56000, 64000, 128000, or 2015232.
http://www.cisco.com/en/US/docs/ios/interface/command/reference/ir_c2.html#wp1011644
so the right choice is 1480000 in your case
I remember clock rates that are then adjusted by the router itself
Hope to help
Giuseppe
