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serial 0/0 is down, line protocol is down

all:

whenever i get a hick up on my T1 to the internet my router interface goes to a "serial 0/0 is down, line protocol is down". Once this happens I'm forced to reboot the router to get the interface back up. I do a 'no shut' but that doesn't work - I have to reboot.

Has anyone seen this before?

router - 2600

ios - 12.2(6r)

thanks

2 REPLIES
Hall of Fame Super Silver

Re: serial 0/0 is down, line protocol is down

Robert

That seems quite strange to me. Usually when a serial interface says the state is down it is an indication that it is not seeing any electrical signals (no DTR, DSR, or anything similar). In my experience it has usually been a hardware issue or a physical connection issue. I am surprised that a reboot of the router brings it back into service. I would wonder about whatever the 2600 is physically connected to. Is it possible that whatever you are connected to gets into a wierd state and gets straightened out when the router reboots?

HTH

Rick

VIP Purple

Re: serial 0/0 is down, line protocol is down

Hello,

in addition to Rick's post, I found the following bug:

CSCdu88223 Bug Details

Serial interface down/down, signaling is up

Symptoms: A serial interface may show an interface as down/down even when

all signals (request to send [RTS], clear to send [CTS], data terminal ready

[DTR], data carrier detect [DCD]) are present.

Conditions: This symptom is observed on the serial interface of a Cisco

router that is running Cisco IOS Release 12.0(15).

Workaround: Reload the microcode.

I searched for bugs in 12.2(6), this appears to be fixed in 12.2(13)T.

Can you check ('with show interface serial') if the signals mentioned are actually there ? If so, you could try and load 12.2(13)T and check if the problem persists...

HTH,

GP

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