Quick question for the GURUS--Frame Relay Switching

mikeybinec

If I enable (config)#frame-relay switching on a router, aren't all the serial interfaces supposed to be DCE, i.e.
(conf-if)#frame-relay intf-type dce or is the supposed dte side allowed to be a dce and the FR Switch can be dte?

Am I making sense?

I'm looking at a Cisco Netacad CCNP lab from 2010 that has one serial interface on the FR is dte and the other end is dce

Thanks

Ltat42a

I think it depends on your cabling. If you want the Frame relay serial ports to be the DCE, you would connect the DCE end of the cable onto those serial ports, the DTE end of the cable on the other end. You can also verify which end is the DCE with the show controllers Serialx/x command.

theodoxa

In the real world, the ISP (Frame Relay Switch) would be the DCE, but I'm not sure that is strictly required for Frame Relay. For HDLC/PPP, it doesn't matter. I have always just made the "ISP" (Frame Relay Switch) end DCE.

TehToG

To understand this you need to know how serial 'works'. DTE stands for data Terminal equipment. This is the end on your terminating device (eg. Cisco router). DCE stands for Data circuit-terminating equipment. This end terminates the isps circuit. Th DCE end provides the clock signal which is an easy way of remembering it.

The clock signal is needed for serial to work so one end must always be DCE and the other DTE. In a lab environment (or your example) we can add a clock signal (via the clock rate command) to one end of a serial connection to simulate this.

mikeybinec

Yeah i understand dce vs dte.. I was under the impression, the FR was ALWAYS the DCE side of link

Thanks all

Ltat42a

In a real world environment, yes, the FR is always the DCE side which is provided by the ISP. In a lab environment, you can use a router as a frame-relay switch and setup a frame relay network. You can decide which end you want to be the DCE.

gorebrush

As above, it's the cable that dictates what end is which, and in the real world, yes the ISP will *always* be DCE.