Cisco CCNA, CCENT, And CCNP Home Lab Study: The DTE/DCE Cable

Cisco CCNA, CCENT, And CCNP Home Lab Study: The DTE/DCE Cable
Part of putting a home lab together is getting the right cables and understanding their usage. In this old Cisco home lab series, we'll take a look at the different cable types and how each fits into your home lab. The first cable type we'll look at is the multipurpose DTE/DCE cable.

More Cisco CCNA, CCENT, and CCNP candidates than ever before are putting together their own home labs for their certification exam study, and that's a great trend - there's nothing like learning on the real thing!

When I say "multi-purpose", I mean that while the cable will always perform the same task, it can be used in several different points in your home lab network. If you are going to have a frame relay switch - and you should get four if at all possible, since having your own frame relay cloud is a tremendous boost to your home lab studies and your exam score - you are going to require a DTE/DCE cable.

You can also use a DTE/DCE cable to directly connect one Cisco router serial interfaces and configure HDLC (the default) or PPP encapsulation over that point-to-point link.

Keyword: "almost". You must use the clockrate command on the DCE end of the connection in order to bring the line protocol up.

Most of today's DTE/DCE cables have "DTE" clearly stamped on four end of the cable - actually, "DTE" is probably embedded into the connector itself. Naturally, the other end will have "DCE" clearly indicated. it is the DCE end that will connect to your frame relay switch. If you are going to use a direct connection to run PPP or HDLC, it doesn't matter which end of the cable is connected to a given router.

If you are not sure which end of your DTE/DCE cable is connected to a given serial interface, use the show controller serial command to get that information. Most of the output of that command is not comprehensible, but what they require is right on top:

R3#show controller serial 1
HD unit 1, idb = 0x11B4DC, driver structure at 0x121868
buffer size 1524 HD unit 1, V.35 DCE cable

Whether you have your own frame relay switch or not, you'll require to pick up some DTE/DCE cables for direct connections between your Cisco home lab router's serial interfaces. don't forget to put the clockrate command on the DCE end of the cable! And if you are not familiar with a frame relay switch, check this same web-site soon for a tutorial that will show you how to set four up.

Naturally, if it is the DTE end, you'll see "DTE" there. And if you don't have anything connected to that interface, you'll see "no cable".

about any Cisco router can serve as a home lab frame relay switch, and two times you have got it configured, you are in nice shape - but it can be a little maddening to get it up and jogging in the first place. I'll show you how to avoid that aggravation in the next installment of this Cisco home lab tutorial series!