Configuring 1DSU-T1 on Cisco 1720

Unanswered Question
Aug 18th, 2007

Hello,

I'm playing with a couple of Cisco 1720's and trying to make them work. Each of them has 1 WIC 1DSU-T1 (http://www.cisco.com/en/US/products/hw/routers/ps221/products_data_sheet09186a00801a9184.html)

I reset both routers and configured onboard FastEthernet interfaces. However, I'm confused about these WIC's. They show up as Serial interfaces and I cannot bring them up.

I tried connecting them to each other and to a laptop via regular CAT5 cross-over cable, but all it shows is

Interface IP-Address OK? Method Status Prot

ocol

FastEthernet0 192.168.3.103 YES manual up down

Serial0 10.0.0.2 YES manual down down

(routers' configuration is provided below)

My questions are:

1. What am I doing wrong? Do I need to set up clock rate, etc for this "serial" interfaces?

2. Can I troubleshoot these 1DSU-T1 WIC's with a cross-over cable and a laptop at all? (Linux 2.6.8 with regular Ethernet interface)

Thanks in advance for any help!

I have this problem too.
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scarabey_ Sat, 08/18/2007 - 16:42

P.S. Here's the routers' configuration:

test1#show interfaces serial 0

Serial0 is down, line protocol is down

Hardware is PQUICC with Fractional T1 CSU/DSU

Internet address is 10.0.0.1/24

MTU 1500 bytes, BW 1544 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, 3 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions

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

test1#show running-config

Building configuration...

Current configuration : 601 bytes

!

version 12.1

no service single-slot-reload-enable

service timestamps debug uptime

service timestamps log uptime

service password-encryption

!

hostname test1

!

!

!

memory-size iomem 25

ip subnet-zero

!

!

!

!

interface Serial0

ip address 10.0.0.1 255.255.255.0

no fair-queue

!

interface FastEthernet0

ip address 192.168.2.104 255.255.255.0

speed auto

!

ip classless

ip http server

!

!

line con 0

login

line aux 0

line vty 0 4

login

!

end

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

test2#show interfaces serial 0

Serial0 is down, line protocol is down

Hardware is PQUICC with Fractional T1 CSU/DSU

Internet address is 10.0.0.2/24

MTU 1500 bytes, BW 1544 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 00:15:29

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

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, 6 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions

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

test2# show running-config

Building configuration...

Current configuration:

!

version 12.1

service timestamps debug uptime

service timestamps log uptime

service password-encryption

!

hostname test2

!

!

!

!

!

memory-size iomem 25

ip subnet-zero

!

!

!

!

interface Serial0

ip address 10.0.0.2 255.255.255.0

no fair-queue

!

interface FastEthernet0

ip address 192.168.3.103 255.255.255.0

speed auto

!

ip classless

ip http server

!

!

line con 0

login

transport input none

line aux 0

line vty 0 4

login

!

no scheduler allocate

end

Richard Burts Sun, 08/19/2007 - 04:30

The biggest problem is your crossover cable. An Ethernet crossover will cross 1, 2 and 3, 6 but a T1 serial crossover will cross 1, 2 and 4, 5. You can not use standard Ethernet crossover to connect serial interfaces.

Once you get a correct crossover cable you will also need to configure one of the routers for clocking internal and to configure a clock rate.

HTH

Rick

rseiler Mon, 08/20/2007 - 11:55

The correct command to see the status of the physical serial port is 'show controller serial'.

Also, the status of the T1 DSU is seen with the command 'show service-module'.

Please note that a Cat5 patch cable may short-out one or both of the CSU's if used to connect back-to-back.

Be sure to *only* use a cable with pins 1,2,4 and 5 connected. *DO NOT* cross-connect *any* other pins!!! A T1 should specifically *not* be grounded on pins 3 or 6, particularly between 2 cross-connected routers.

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