# Dcd=down Dsr=down Dtr=up Rts=up Cts=up



## lAwBoY (Nov 11, 2005)

have a router connected to the external CSU

ROUTER -<---> CSU <----> SmartJack

my telco has tested good to the CSU when doing a loop to the CSU 
but on the router am seeing that on the main interface

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

what does this explain

Router or cable or csu problem?


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## Rockn (Jul 29, 2001)

DCD down indicates no signal from the CSU and DSR will not be up until there is a signal.


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## lAwBoY (Nov 11, 2005)

What does this DTR=up RTS=up CTS=up mean then

You mention that that router not receiving a signal from CSU
Can i say that the fault is likely to be either the CSU or the cable


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## StumpedTechy (Jul 7, 2004)

DTR is Data Terminal Ready
RTS is Request to Send
CTS is Clear to Send

and just to explain the 2 that are down - Data carrier detect and Data set ready.

The data set can't be ready if there is no Data carrier detected. This really can be a problem in 3 places router with a bad WIC - cable (doubful usually cables don't "go bad") or CSU.


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## lAwBoY (Nov 11, 2005)

i understand we can use loopback test to isolate the fault to check if the equpiment are fine.

I have diffcuitly understand when they mention loop back facing where.. and loopback from..

what do each mean and what the difference

if i can use the external csu to loop toward the router... and the loop is good.. this would clear the cable , csu and wic right?


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## StumpedTechy (Jul 7, 2004)

Usually a loopback plug has to be inserted somewhere. if this is the case you could do it at the end of the cable and then run the test from the router and this would clear both the router and the cable and leave the CSU on down as the problem.


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## O111111O (Aug 27, 2005)

It's probably your CSU, or the Telco flipped at the smartjack. You can also do this with the Telco, creating a hardloop using the cable that went into your CSU.

Make a hard-loop cable for your CSU, see what that does.

RJ-45 pin
cable 1-4
cable 2-5

Plug that into the DS1 line port of your CSU.

Here's a Cisco reference.

http://www.cisco.com/warp/public/471/hard_loopback.html


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