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Debugging a T1 Connection

I am a programmer with a small company so I also have to wear the hat of systems admin, helpdesk, and network engineer.  I know enough about networking to be dangerous so if you will take the time to answer please put it in simple language as I don't speak much network

I inherited a setup with 3 T1's from one provider (multilinked) all working well, and 2 T1's from another provider where only one of the circuits has ever worked.  My mission is to get the second T1 from this provider working.

Things I think might be wrong but do not know how to determine as right or wrong are the hardware differences of the modules/carriages/whatever those boards are called that the csu/dsu's plug into as well as the csu/dsu's themselves seem to be different flavors.

The All of the T's on Serial0 work, the one on Serial1 does not.  Also I am not using the Ethernet interfaces on the Serial1 either.

Pasting the inventory, config, and show interface results;

#sho inv
NAME: "3845 chassis", DESCR: "3845 chassis"
PID: CISCO3845         , VID: V01 , SN: FTX1032A4RL

NAME: "c3845 Motherboard with Gigabit Ethernet on Slot 0", DESCR: "c3845 Motherb                                                                                                                                                             oard with Gigabit Ethernet"
PID: CISCO3845-MB      , VID: V05 , SN: FOC102813RM

NAME: "WAN Interface Card - HWIC CSU/DSU on Slot 0 SubSlot 0", DESCR: "WAN Inter                                                                                                                                                             face Card - HWIC CSU/DSU"
PID: HWIC-1DSU-T1      , VID: V02 , SN: FOC151211ZL

NAME: "WAN Interface Card - HWIC CSU/DSU on Slot 0 SubSlot 1", DESCR: "WAN Inter                                                                                                                                                             face Card - HWIC CSU/DSU"
PID: HWIC-1DSU-T1      , VID: V02 , SN: FOC16024D9B

NAME: "WAN Interface Card - HWIC CSU/DSU on Slot 0 SubSlot 2", DESCR: "WAN Inter                                                                                                                                                             face Card - HWIC CSU/DSU"
PID: HWIC-1DSU-T1      , VID: V02 , SN: FOC15343KES

NAME: "WAN Interface Card - HWIC CSU/DSU on Slot 0 SubSlot 3", DESCR: "WAN Inter                                                                                                                                                             face Card - HWIC CSU/DSU"
PID: HWIC-1DSU-T1      , VID: V02 , SN: FOC152927YY

NAME: "FastEthernet/WAN on Slot 1", DESCR: "FastEthernet/WAN"
PID: NM-2FE2W=         , VID: 1.0, SN: JAD061702EY

NAME: "WAN Interface Card - DSU/CSU T1 Fractional (V2) on Slot 1 SubSlot 0", DESCR: "WAN Interface Card - DSU/CSU T1 Fractional (V2)"
PID: WIC-1DSU-T1-V2      , VID: 1.1, SN: FOC09021HWJ

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


interface Serial0/3/0
description Sprint T1 #1 circuit xxxxxx
bandwidth 1544
no ip address
encapsulation ppp
no fair-queue
ppp multilink
ppp multilink group 2

interface Serial1/0/0
description Sprint T1 #2 circuit xxxxxx
bandwidth 1544
no ip address
encapsulation ppp
no fair-queue
ppp multilink
ppp multilink group 2

interface Multilink2
ip address xxx.xxx.xxx.xxx 255.255.255.252
ip access-group 100 in
ppp multilink
ppp multilink group 2
ppp multilink fragment disable
no cdp enable

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

Serial0/3/0 is up, line protocol is up
  Hardware is GT96K with integrated T1 CSU/DSU
  Description: Sprint T1 #1 Ckt
  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Open, multilink Open
  Link is a member of Multilink bundle Multilink2, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:05, output 00:00:01, output hang never
  Last clearing of "show interface" counters 2d20h
  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
     157480 packets input, 36418885 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     4670 input errors, 4652 CRC, 1 frame, 14 overrun, 0 ignored, 3 abort
     393959 packets output, 27849179 bytes, 0 underruns
     0 output errors, 0 collisions, 15 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     3 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

Serial1/0/0 is down, line protocol is down
  Hardware is DSCC4 with integrated T1 CSU/DSU
  Description: T1 #2
  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
     reliability 253/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Closed, loopback not set
  Keepalive set (10 sec)
  Last input 2d18h, output 2d18h, output hang never
  Last clearing of "show interface" counters 2d20h
  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
     22465 packets input, 7503982 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 3 giants, 0 throttles
     11 input errors, 4 CRC, 6 frame, 0 overrun, 0 ignored, 1 abort
     1867 packets output, 65014 bytes, 0 underruns
     0 output errors, 0 collisions, 8288 interface resets
     3 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     4 carrier transitions
     DCD=down  DSR=up  DTR=up  RTS=up  CTS=down

Multilink2 is up, line protocol is up
  Hardware is multilink group interface
  Internet address is xxxx.xxx.xxx.xxx/30
  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Open, multilink Open
  Open: IPCP, loopback not set
  Keepalive set (10 sec)
  DTR is pulsed for 2 seconds on reset
  Last input 00:00:00, output never, output hang never
  Last clearing of "show interface" counters 2d20h
  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
     66497 packets input, 34697205 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     33 input errors, 0 CRC, 26 frame, 0 overrun, 0 ignored, 7 abort
     344710 packets output, 27062452 bytes, 0 underruns
     0 output errors, 0 collisions, 2 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions

Everyone's tags (4)
2 REPLIES

Re: Debugging a T1 Connection

You're going to have to post the entire config, but in general because of t1 clock timing I don't think you want to mix controllers in the motherboard with controllers in the module slot of the router. The motherboard shares one timing clock and the slot module uses it's own. Also do some sh serial 1/0/0 service-module commands to see if you have a red alarm. If you do contact the carrier.

Sent from Cisco Technical Support iPad App

New Member

Debugging a T1 Connection

Thank you for your response.  This did turn out to be a telco problem and is now resolved.

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