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serial up line protocol down

jjbo jjbo is offline
Junior Member
Join Date: Jun 2008
Posts: 1
Need help on finding a reason for interface down protocol down...
Did a loop back test with hdlc on the circuit but didn't get it looped.

Please let me know if you have any thoughts.

This router has got an integerated csu dsu, all the pinouts (dcd rts cts dsr dtr) are up, still the interface is up and protocol is down.

Cisco#show interf ser 1/0
Serial1/0 is up, line protocol is down
Hardware is QUICC with integrated T1 CSU/DSU
Internet address is a.b.c.d/30
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, loopback set
Keepalive set (10 sec)
Last input 14:41:56, output 00:00:00, output hang never
Last clearing of "show interface" counters 00:06:25
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
1 input errors, 0 CRC, 0 frame, 0 overrun, 1 ignored, 0 abort
81 packets output, 1134 bytes, 1 underruns
1 output errors, 0 collisions, 20 interface resets
0 output buffer failures, 0 output buffers swapped out
2 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up

================================================== ==
debug serial interface

Jun 24 13:50:21.086 UTC: Serial1/1: attempting to restart
Jun 24 13:50:46.454 UTC: Serial1/0: attempting to restart
Jun 24 13:50:51.094 UTC: Serial1/1: attempting to restart
Jun 24 13:51:16.455 UTC: Serial1/0: attempting to restart

sh controllers serial 1/0
Interface Serial1/0
Hardware is Quicc 68360 with Integrated FT1 CSU/DSU module
TX clock detected.
idb at 0x61D3DF9C, driver data structure at 0x61D43EF8
WIC interrupt reg = F
SCC Registers:
General [GSMR]=0x2:0x00000930, Protocol-specific [PSMR]=0x8
Events [SCCE]=0x0000, Mask [SCCM]=0x001F, Status [SCCS]=0x0003
Transmit on Demand [TODR]=0x0, Data Sync [DSR]=0x7E7E
Interrupt Registers:
Config [CICR]=0x00C9CF00, Pending [CIPR]=0x00000002
Mask [CIMR]=0xE0004400, In-srv [CISR]=0x00000000
SDMA Registers:
[SDSR]=0x00, [SDAR]=0x03B8F3E8, [SDCR]=0x0772
Command register [CR]=0x640
Port A [PADIR]=0x0000, [PAPAR]=0xFFFF
[PAODR]=0x0000, [PADAT]=0xACFB
Port B [PBDIR]=0x0013FE, [PBPAR]=0x00000E
[PBODR]=0x000000, [PBDAT]=0x03CC5C
Port C [PCDIR]=0x0002, [PCPAR]=0x000C
[PCSO]=0x00A0, [PCDAT]=0x0FCD, [PCINT]=0x0001
Receive Ring
rmd(3D010420): status 9000 length 60C address 3B380A4
rmd(3D010428): status 9000 length 60C address 3B39AA4
rmd(3D010430): status 9000 length 60C address 3B3A124
rmd(3D010438): status 9000 length 60C address 3B3A7A4
rmd(3D010440): status 9000 length 60C address 3B3AE24
rmd(3D010448): status 9000 length 60C address 3B39424
rmd(3D010450): status B000 length 60C address 3B3B4A4
Transmit Ring
tmd(3D010458): status 5C00 length 44 address 3B8F3D4
tmd(3D010460): status 5C00 length 18 address 3B8F3D4
tmd(3D010468): status 5C00 length 18 address 3B911D4
tmd(3D010470): status 5C00 length 44 address 3B911D4
tmd(3D010478): status 0 length 18 address 0
tmd(3D010480): status 0 length E address 0
tmd(3D010488): status 2000 length E address 0

Rx BD Base [RBASE]=0x420, Fn Code [RFCR]=0x18
Tx BD Base [TBASE]=0x458, Fn Code [TFCR]=0x18
Max Rx Buff Len [MRBLR]=1548
Rx State [RSTATE]=0x0, BD Ptr [RBPTR]=0x420
Tx State [TSTATE]=0x18000348, BD Ptr [TBPTR]=0x478

CRC Preset [C_PRES]=0xFFFF, Mask [C_MASK]=0xF0B8
Errors: CRC [CRCEC]=0, Aborts [ABTSC]=0, Discards [DISFC]=0
Nonmatch Addr Cntr [NMARC]=0
Retry Count [RETRC]=0
Max Frame Length [MFLR]=1608
Rx Int Threshold [RFTHR]=0, Frame Cnt [RFCNT]=65532
User-defined Address 0000/0000/0000/0000
User-defined Address Mask 0x0000

buffer size 1524
QUICC SCC specific errors:
806954 input aborts on receiving flag sequence
0 throttles, 0 enables
0 overruns
1 transmitter underruns
0 transmitter CTS losts

Issue 2

Same as above with a slight difference.

Its running clean while testing a hard loopback plug on it, no packet drops, no errors but its flapping in every 2 hrs.

Thanks in advance...


Last edited by jjbo; 06-24-2008 at 03:48 PM..
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