Serial is up, line protocol is down (looped) - What does this mean?

[Motopsycho]

I am currently trying to turn-up a fractional T1 from a Cisco 7206VXR router and I cannot figure out why I am showing line protocol down when the circuit has been looped. Normally I would see up/up (looped) on a good circuit with a hard loop. I've changed the encaps to HDLC and back to PPP a number of times with no luck. From my experience when the line protocol is down, it usually means an encapsulation mismatch or the number of ds0s do not match on both sides. The down-when-looped command is not configured on this interface and would I think would show down/down looped if it were. Can anyone explain this?

Serial5/0/16:0 is up, line protocol is down (looped)
Hardware is PA-MC-2T3+
MTU 1500 bytes, BW 512 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, LCP REQsent, crc 16, loopback not set
Last input 00:00:00, output 12w0d, output hang never
Last clearing of "show interface" counters 00:03:34
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/1/16 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
Available Bandwidth 384 kilobits/sec
5 minute input rate 0 bits/sec, 1 packets/sec
5 minute output rate 0 bits/sec, 1 packets/sec
40 packets input, 560 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
5 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 5 abort
40 packets output, 560 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions no alarm present
Timeslot(s) Used: 1-8, subrate: 512Kb/s, transmit delay is 0 flags
non-inverted data

 

[mainstreetexpress]

Hi
This happens becasue you are running PPP encapsulation. If there is a hardware loopback on the CCT somewhere it will show
Serial5/0/16:0 is up, line protocol is down (looped)
This is perfectly normal in PPP

Just try and change the encapsulation to HDLC and see what happens, both line and protocol should come up

Cheers

Mark

 

[Motopsycho]

I knew PPP would cause a different line protocol condition when a hard loop was put up, but I have also changed the encaps to HDLC and that shows down/down. In the past I have been able to see loops using PPP encaps and showing an up/up condition. Any other suggestions?