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New Member

Problems with point-to-point T1 line

I am having problems with a point-to-point T1 line I recently had installed between two of my locations. I'm getting a carrier detect light and an alarm light on the WIC-1DSU-T1 cards in my routers. I've also got a TLOS light on the Smart-Jack. I've had the telco provider come out and test everything from the line into the buildings to the smart-jack, looped successfully between the smart-jacks, etc. I have swapped out cables and tested demarc extensions successfully. I have also successfully performed software loopback tests and a hardware loopback test with a loopback plug on the CSU/DSU cards. I'm stuck here and getting frustrated. Can anyone provide feedback on where the problem might be? Any assistance or feedback at this point would be greatly appreciated.

Here is some text from commands ran on the router:

--from 'show int s2/0' command

Serial2/0 is down, line protocol is down

Hardware is DSCC4 with integrated T1 CSU/DSU

Description: Disaster Recovery point-to-point T1 #2 (16/HCGS/006432/TWCS)

Internet address is 10.10.50.5/30

MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec,

reliability 228/255, txload 1/255, rxload 1/255

Encapsulation HDLC, loopback not set

Keepalive set (10 sec)

Last input never, output 20:58:24, output hang never

Last clearing of "show interface" counters 21:17:21

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

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

305973 input errors, 35481 CRC, 270492 frame, 0 overrun, 0 ignored, 0 abort

15 packets output, 2537 bytes, 0 underruns

0 output errors, 0 collisions, 2544 interface resets

0 output buffer failures, 0 output buffers swapped out

6 carrier transitions

DCD=down DSR=up DTR=up RTS=up CTS=down

*****************************************************************

--from 'show controllers' command

Interface Serial2/0

Hardware is DSCC4 with Integrated FT1 CSU/DSU module

TX and RX clocks detected.

idb at 0x62D88CF8, driver data structure at 0x62D90804

DSCC4 Global Registers:

GCMDR=0x00000000, GSTAR=0x00000000, GMODE=0x000B0005

IQLENR0=0x11111111, IQLENR1=0x00110000

IQCBAR=0x0598FBA0, IQPBAR=0x0598FA60

FIFOCR1=0x42104000, FIFOCR2=0xBDEEB800, FIFOCR3=0x0000000F, FIFOCR4=0x08080808

SCCRXBAR=0x0598F060, SCCTXBAR=0x0598F560

CHCFG=0x04000000, CHBRDA=0x0598FF60, CHBTDA=0x059903A0

FRDA=0x0598FF60, FTDA=0x059903A0, LRDA=0x00000000, LTDA=0x059903A0

SCC Registers:

STAR=0x00300000, CCR0=0x80000000, CCR1=0x02568000, CCR2=0x08050008

ACCM=0x00000000, IMR(s)=0xFFFAFF7C, RLCR(s)=0x00008032, SYNCR(s)=0x00000000

CMDR(s)=0x01010000 (last command), TCR(s)=0x00000000, TIMR(s)=0x00000000

TTSA=0x00000000, RTSA=0x00000000, PCMMTX= 0x00000000, PCMMRX=0x00000000

LBI registers:

LCONF=0x804003FD

SSC registers:

SSCCON=0x0000C63F, SSCBR=0x0000000F, SSCTB=0x00000000, SSCRB=0x0000FFFF

SSCCSE=0x00000000, SSCIM=0x00000002

GPP registers:

GPDIR=0x000044EF, GPDATA=0x000074F0, GPIM=0x0000F7FF

FPGA/LBPLD Registers: FVR=0xA9, FISR=0x00, LISR=0x00, LMISC=0x50

W00S:0xE2, W01S:0xAA, W10S:0xE2, W11S:0xAA

FPGA shadow registers:

NBCKSL:0xE4, DPM:0xE4, FISR:0x00, LCS:0x00, R8KSL:0x00

DCKSL:0x0, FIMR:0x0, FVR:0x0, DTC:0x0

W00S:0x0, W00M:0x33, W00C:0x0, W01S:0x0, W01M:0x0, W01C:0x80, WMS0:0x1

W10S:0x0, W10M:0x33, W10C:0x0, W11S:0x0, W11M:0x0, W11C:0x80, WMS1:0x1

TCR0:0x0, TCR1:0x0

last_rxbd(age) 0x05990320(0), last_rxbd_next 0x05990340, prev_last_rxbd 0x000000

00

DSCC4 SCC specific errors:

0 input aborts on receiving flag sequence

0 throttles, 0 enables

0 overruns

0 transmitter underruns

0 transmitter CTS losts

0 dma tx err, 0 dma rx err

53 scc frame length exceeded

0 xoffs received

1065038 fecpm intr, 820404 rx intr, 36 tx intr, 0 num holdq

0 rxbd overflow

5 REPLIES
New Member

Re: Problems with point-to-point T1 line

What is the encapsulation on the other side of the circuit? Is it HDLC also? Can you post the interface configurations for both sides of the circuit.?

bcbv

New Member

Re: Problems with point-to-point T1 line

Yes, it is HDLC also. I was trying to use PPP, but switched to HDLC trying to get the simpliest configuration possible. Perhaps I'm off though. Let me know if any other information would be helpful and I'll post.

Circuit config on side A

--------------------------------

interface Serial0/0

description point-to-point T1 (16/HCGS/006431/TWCS)

ip address 10.10.50.6 255.255.255.252

no ip route-cache

no ip mroute-cache

no fair-queue

Serial0/0 is down, line protocol is down

Hardware is DSCC4 with integrated T1 CSU/DSU

Description: Disaster Recovery point-to-point T1 #1 (16/HCGS/006431/TWCS)

Internet address is 10.10.50.2/30

MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation HDLC, loopback not set

Keepalive set (10 sec)

Last input never, output never, 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

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

0 packets output, 0 bytes, 0 underruns

0 output errors, 0 collisions, 7 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions

DCD=down DSR=up DTR=up RTS=up CTS=down

Circuit config on side B

--------------------------------

interface Serial2/0

description point-to-point T1 (16/HCGS/006432/TWCS)

ip address 10.10.50.5 255.255.255.252

no ip route-cache

no ip mroute-cache

no fair-queue

Serial2/0 is down, line protocol is down

Hardware is DSCC4 with integrated T1 CSU/DSU

Description: Disaster Recovery point-to-point T1 #2 (16/HCGS/006432/TWCS)

Internet address is 10.10.50.5/30

MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec,

reliability 228/255, txload 1/255, rxload 1/255

Encapsulation HDLC, loopback not set

Keepalive set (10 sec)

Last input never, output 00:49:49, output hang never

Last clearing of "show interface" counters 01:08:46

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

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

305973 input errors, 35481 CRC, 270492 frame, 0 overrun, 0 ignored, 0 abort

15 packets output, 2537 bytes, 0 underruns

0 output errors, 0 collisions, 127 interface resets

0 output buffer failures, 0 output buffers swapped out

6 carrier transitions

DCD=down DSR=up DTR=up RTS=up CTS=down

New Member

Re: Problems with point-to-point T1 line

Something wrong with router A. The ip address is 10.10.50.6 but in the show int command it shows as 10.10.50.2?!? Are you sure on the configs? maybe looking at the wrong router? Also you did not include the encasulation command in the configs although it does show the encapsulation type in the show int. I think that the show int does not cereespond to the interface config for router A.

bcbv

New Member

Re: Problems with point-to-point T1 line

Sorry, I took the configs above from captures I have done while troubleshooting. I changed the IP address at one point to put the interfaces of the two routers on different subnets. The IP address of 10.10.50.6 is the correct IP for the current configuration. As for the encapsulation command not showing, it seems to omit any entries which it considers to be default when you look at the configuration. If I change the encapsulation type to PPP, it shows that entry when I look at the config. It also does this for other commands such as timeslots, framing, linecode, etc. Also, both routers are running IOS version 12.2(11)T8 if that helps any.

Silver

Re: Problems with point-to-point T1 line

What you need to do is work with the carrier . Have the carrier give you a loop from the smartjack back at the remote location back to you , you should see the router int go up up looped, If this happens then you know that from the remotre smart jack to the router you have a good circuit. If you do not , have the carrier go to the other smart jack and give a loop facing the remote location , you should see the line go up up looped. If you do not then this proves it is a carrier problem or a cabling problem on extended demarc ..

first test

routera ----SJa -------cloud---------SJb--------ext demarc--------router b

have carrier loop sjb towards routera a

if you see up up (looped) on serial int of routera you have a good circuit from SJ B to router a

2nd test

routera ----SJa -------cloud---------SJb--------ext demarc--------router b

have carrier loo SJ a towards router B if you do not see loop in router B then you have a problem on extended demarc.

make sure that the 'down when looped' command is not on the serial interfaces of the routers .

before you start playing with encap , this is layer 2 , you need to get layer 1 working .

carriers can give loops from diffrerent places in network including the smart jacks.

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