Assuming this is a point-to-point connection and you have an internal T1 DSU/CSU WIC, the first thing you want to do is figure out how the DSU/CSU is configured now. Run the "show service-module" command and copy/save this information. You will see something like this:
Cisco2620XM#show service-module serial 0/0
Module type is T1/fractional
Hardware revision is 0.128, Software revision is 0.2,
Image checksum is 0x73D70058, Protocol revision is 0.1
Receiver has no alarms.
Framing is ESF, Line Code is B8ZS, Current clock source is line,
Fraction has 24 timeslots (64 Kbits/sec each), Net bandwidth is 1536 Kbits/sec.
Last module self-test (done at startup): Passed
Last clearing of alarm counters 9w0d
loss of signal : 0,
loss of frame : 0,
AIS alarm : 0,
Remote alarm : 1, last occurred 9w0d
Module access errors : 0,
Total Data (last 96 15 minute intervals):
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 2 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
Data in current interval (408 seconds elapsed):
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
Cisco2620XM#
Note that this information is from a full T1. If you are running a true fractional T1 connection, then the number of timeslots used will be less than 24 and your net bandwidth will be less than 1536 Kbits/sec.
If you need to increase the number of timeslots, go into config mode and enter the following:
interface serial 0/0
service-module t1 timeslots 1-24 speed 64
end
Don't forget to save your configuration ("write memory" or "copy running-config startup-config").
A helpful link:
Use WIC-1DSU-T1 Interface Cards on Cisco 1600, 1700, 2600, 3600 and 3700 Series Routers
http://www.cisco.com/en/US/products/hw/modules/ps3129/products_tech_note09186a0080093d70.shtml
You should plan and coordinate activation with your service provider ahead of time, so they can enable the additional channels on the line while you configure the timeslots on the router.
Another note: if you have a Frame Relay T1 (if you see "encapsulation frame-relay" under your serial interface's configuration), then you may have a full T1 access link but only a sub-T1 Committed Information Rate (CIR) across that connection. In this case, you need to work with your service provider to either increase the CIR on your Permanent Virtual Circuit (PVC), or convert the link to a dedicated point-to-point full T1 leased line.
