We have a 1750-2v (with 2A/S card having S0 & S1 as serial ports) router with S1 on 64kbps leased line to the remote location. We are facing problem as the link went down 2 days back. The troubleshooting shows the RAD ASM-20 (v.35-CPE) modem status as TD=off ,RD=on,DCD=on,RTS=on. & the SH CONTR S1 output shows third line as DTE Unknown (13) clocks stopped.
Can anyone help in diagnosing & locating the faulty segment? (i.e router serial port or DTE cable or v.35 modem or problem is at telecom service provider's end ?)
This looks like an interface issue. As TD is off no signal is transferred from the interface to the modem. If RD is off means modem cloak is faulty orit can be line. But here RD is on. Only TD is off in the RAD ASM20.So it is sure that the cable or Interface is the issue. Try changing the interface card or cable. First give a local loop in the ASM 20 and check the show interface command .If show interface command show the interface status as looped, then interface is fine. If its not showing looped it is an interface issue.
If the interface gets looped and then also the issue continues, then check the interface cable. If that also is fine ,then you can take the help of the service provider.
Show int doesn't show int status as looped. Hence it seems the interface is the issue.But if this is the case then why such thing(interface going down) should happen? What are the possibilities that serial port/interface (serial 2A/S) goes down?
Any specific precaution needs to be taken in future?
Its almost sure that interface is the culprit. But before that, let me know onething. Have you tried changing the cable? If not, do so and see if the same issue continues.
There are few reasons that make the interface go bad.
1. The hardware failure.
2. The surge attack from the line connected to the interface.
3. Handling of interfaces with router powered on.
4. The motherboard/chassis or an IOS issue.
The 4'th option is the worst case which occurs very rarely. So you check out the power system, and also the last mile ,if it is on a copper pair.You can put a surge arrester to resist any surge attacks. You can insert it into the krone box. Hope this answered your question.
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