re two flavors of DS3: clear-channel and channelized. Typically, clear- channel DS3s are used for data links, and channelized DS3s are used for voice links. The configurations in this section assume an integrated CSU/DSU in all cases. If you have an older router that requires an external CSU/DSU, you'll probably have a High- Speed Serial Interface (HSSI-pronounced hissy), which still looks like a serial interface within IOS. The difference will be that you cannot configure framing on a HSSI port Additionally, because the CSU/DSU (which counts and reports these errors) is an ex- ternal device, you won't be able to see DS3 errors on a HSSI port. Clear-Channel DS3 Configuring a clear-channel DS3 is a pretty boring affair. Specify the framing with the framing interface command, and then configure the interface like any other serial interface: interface Serial3/1/0 description DS3 ip address 10.100.100.100 255.255.255.252 framing c-bit Configuring DS3s You show the status of the interface the same as you do for any other interface. The errors and counters are generic, and not DS3- or even telecom-specific: 7304#sho int s3/1/0 Serial3/1/0 is up, line protocol is up Hardware is SPA-4XT3/E3 Description: DS3 Internet address is 10.100.100.100/30 MTU 4470 bytes, BW 44210 Kbit, DLY 200 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, crc 16, loopback not set Keepalive set (10 sec) Last input 00:00:02, output 00:00:01, output hang never Last clearing of "show interface" counters 6d03h Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: Queueing strategy: fifo Output queue: 0/40 (size/max) 5 minute input rate 101000 bits/sec, 179 packets/sec minute output rate 98000 bits/sec, 170 packets/sec 81589607 packets input, 2171970011 bytes, 0 no buffer Received 61914 broadcasts (229394 IP multicast) 1072 runts, 0 giants, 0 throttles 0 parity 1136 input errors, 10 CRC, 0 frame, 0 overrun, 0 ignored, 54 abort 80620669 packets output, 1165631313 bytes, 0 underruns o output errors, 0 applique, 0 i