PDA

View Full Version : DCE/DTE cable commutative?

markkn
07-25-2009, 11:01 AM
I have a typical setup with a couple of 2501s with the serial ports connected with a combined dce/dte cable. Now my understanding is that such cables simply have the transmit/receive wires switched at one end.

My qestion is this: Are these cables commutative? That is, does it matter which serial interface gets the dte and which gets the dce end. With an rj45 crossover cable this doesn't matter, but these cable companies go throught he effort of putting the labels on each end of the serial cable, so I was wondering.
Big Evil
07-25-2009, 12:05 PM
When you put the DCE or DTE end in a router the interface picks up what end the cable is. If you do a show controllers before and after you will see.

It depend on you set up which end you wish to perform the clock rate.

HTH.
markkn
07-25-2009, 12:49 PM
Excellent! So, its a bit more than simply a crossover. I will dig into that.
Fuzz
07-27-2009, 06:36 AM
Essentially you connect the DCE end to your equipment and the DTE end to the service providers equipment. The DTE end has to provide clocking.
markkn
07-27-2009, 07:07 AM
Thanks for the clarification. This is one of those setups where a combined dce/dte cable connects two 2501s together to simulate a wan link. So its a three foot cable with dce written on one end and dte on the other.
Big Evil
07-27-2009, 08:59 AM
Three feet!
Fuzz
07-27-2009, 10:18 AM
Essentially you connect the DCE end to your equipment and the DTE end to the service providers equipment. The DTE end has to provide clocking.

Ooops, I meant the other way round. DCE end for clocking. Sorry :eek:
markkn
08-03-2009, 09:40 PM
When you put the DCE or DTE end in a router the interface picks up what end the cable is. If you do a show controllers before and after you will see.

It depend on you set up which end you wish to perform the clock rate.

HTH.


I did and I saw. Thanks. Now I am curious how the cables are wired that the 2501 can tell which end is which. Must be some jumpering.
crissa
08-04-2009, 12:57 AM
I did and I saw. Thanks. Now I am curious how the cables are wired that the 2501 can tell which end is which. Must be some jumpering.

Hello,
see <http://www.cisco.com/en/US/docs/routers/access/2500/software/user/guide/cables.html#wp1982>, please.
Bye, Tore