I just set up - for the first time - a serial connection between my two routers. I used T1 CSU/DSUs in each router with a T1 crossover cable between them. I specifically remember reading that you must set the clock rate on one router or the other, but I didn't do that. It's working anyways.
1721-1#show interface s0
Serial0 is up, line protocol is up
Hardware is PQUICC with Fractional T1 CSU/DSU
Internet address is 172.18.21.1/30
MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set
Keepalive set (10 sec)
Last input 00:00:09, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
194 packets input, 13104 bytes, 0 no buffer
Received 178 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
200 packets output, 13605 bytes, 0 underruns
0 output errors, 0 collisions, 10 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out
2 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up
Is that the wrong command to see which side is DCE and which side is DTE? Why did it automatically go to 1544 Kbit/sec without me fooling with the clocking? Is that standard behavior?