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Community Member

Can't ping Serial Interfaces!?

Yo, I just got a 2507 router with 1 ethernet, 2 Serial Interfaces and I can't get either Serial to work. I've tried the basic [ip add, no shut, clock rate, bandwidth] configerations but no matter what I do it always says "Serial1 is down, Line protocal is down" when I do a [show int]. I can't ping the interface and when I do a [show ip route] it only shows the ethernet network. Any suggestions or are the interfaces faulty?

Thanks,

Yami

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Accepted Solutions
Community Member

Re: Can't ping Serial Interfaces!?

Have you connected the serial interfaces to any other router with a serial cable. If no, all above commands go waste. Make one end of serial as DCE ( clockrate) and other as DTE( no clockrate). Ethernet has a feature which makes ethernet up line up if u have "no keepalive" command even though u have no devices on the segment, but that doesnt work on serial interfaces.

6 REPLIES
Community Member

Re: Can't ping Serial Interfaces!?

Have you connected the serial interfaces to any other router with a serial cable. If no, all above commands go waste. Make one end of serial as DCE ( clockrate) and other as DTE( no clockrate). Ethernet has a feature which makes ethernet up line up if u have "no keepalive" command even though u have no devices on the segment, but that doesnt work on serial interfaces.

Community Member

Re: Can't ping Serial Interfaces!?

There's no cabling at all. I'm trying to say that I can't even bring the interface up at all! I'm losing my hair trying to figure out why I can't bring either of the Serial interfaces up to even ping them from the router itself.

Community Member

Re: Can't ping Serial Interfaces!?

You cant get a serial interface up unless u have a serial to serial connection(DTE/DCE connection). You will need a clock synchronisation between serial interfaces to make them up.Hence they are called sync serial. No use pulling your hair or whatever....

Community Member

Re: Can't ping Serial Interfaces!?

Ok, I've got the DCE/DTE lab cable. The two 2507's are connected via the Serials. Now, I've got the ip addresses of 10.0.0.2/8 and 20.0.0.2 /8 in, the no shuts and I've put the clock rate/bandwitdh on the DCE. How do I enable the clock synchronisation?

Community Member

Re: Can't ping Serial Interfaces!?

Plz configure as below

Assuming R1 S0 as DCE:

int s0

no shut

clock rate 56000

ip address 10.1.1.1 255.0.0.0

R2 as DTE: int s0

no shut

ip address 10.1.1.2 255.0.0.0

I hope that you have connected the DCE end of cable to R1 s0, you can check it by issuing "show controllers s 0"

R1>sh controllers s 0

HD unit 1, idb = 0x113170, driver structure at 0x119008

buffer size 1524 HD unit 1, V.35 DCE

cable

R2 s0 will show you as DTE cable.

Once your layer 2 is up, u can ping successfully

Community Member

Re: Can't ping Serial Interfaces!?

Ok, I did what you suggested and actully it didn't work. However, I took your advice on the clock sync command and applyed the [dce-terminal-timing-enable] command to both Serial Interfaces and boom everything works perfectly. Thanks a million. The entire configeration is below:

RouterA

----

DeathWing>en

DeathWing#

DeathWing#conf t

Enter configuration commands, one per line. End with CNTL/Z.

DeathWing(config)#int s0

DeathWing(config-if)#ip add 30.0.0.1 255.0.0.0

DeathWing(config-if)#no shut

DeathWing(config-if)#dce

DeathWing(config-if)#dce-terminal-timing-enable DeathWing(config-if)#Z^

DeathWing#show int

Serial0 is up, line protocol is up

Hardware is HD64570

Internet address is 30.0.0.1/8

MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec,

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

Encapsulation HDLC, loopback not set

Keepalive set (10 sec)

Last input 00:00:08, output 00:00:07, output hang never

Last clearing of "show interface" counters never

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

811 packets input, 48757 bytes, 0 no buffer

Received 785 broadcasts, 0 runts, 0 giants, 0 throttles

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

840 packets output, 52637 bytes, 0 underruns

0 output errors, 0 collisions, 8 interface resets

0 output buffer failures, 0 output buffers swapped out

14 carrier transitions

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

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