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In the Cisco Packet Tracer we also see the Serial DCE and Serial DTE:

enter image description here

but I don't know what's the difference between them.

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3 Answers 3

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One side of the link (DCE), has to transmit the clock signal, which controls the data rate, and the other side (DTE) receives the clock signal.

R1 is DCE here:

interface Serial0/0/0
 ip address 10.0.0.1 255.255.255.252
 clock rate 2000000

R2 is DTE here:

interface Serial0/0/0
 ip address 10.0.0.2 255.255.255.252

The difference between the two cables in packet tracer is just which side you click first:

enter image description here

  • With the DCE cable, (red zigzag with clock) the side you click first will be the DCE, the second will be DTE
  • With the DTE cable (red zigzag no clock) the side you click first will be DTE, the second will be DCE

Whichever way you do it, you'll see one side of the cable shows the clock symbol: this is the DCE.

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DCE stands for data circuit-terminating, data communications, or data carrier equipment - this is a modem or more generally, a line adapter.

DTE stands for data terminal equipment which generally is a terminal or a computer.

Basically, these two are the different ends of a serial line.

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  • In the real world, whether there are DCE Serial line and DTE Serial line?
    – 26334_zeal
    Nov 27, 2018 at 9:32
  • On a console connection, the DCE may be a switch or router, and the DTE is a computer. With a data link, both sides may be configurable.
    – Zac67
    Nov 27, 2018 at 9:38
  • Are you sure about that @Zac67? Cisco RJ-45 console and aux ports are DTE, as they have TXD as output; 25-pin console is DCE, aux is DTE. cisco.com/c/en/us/support/docs/routers/7000-series-routers/… 9-pin on eg SG-300 switch is male, believed DTE.
    – jonathanjo
    Nov 29, 2018 at 23:24
  • @jonathanjo I'm not quite sure about Cisco's parlance - a console port on a switch is in the DCE role and connects to a DTE. Cisco specifies a "rolled cable" (=crossover aka null-modem) which allows for the required DTE-pinout to DTE-pinout connection - there's no general standard for 8P8C serial ports and that's Cisco's way to do it.
    – Zac67
    Nov 30, 2018 at 16:08
  • @Zac67 Cisco defines the 8P8C console and aux sockets as DTE, with CTS, DTR and TXD outputs, and RXD, DSR, RTS as inputs, also explicitly described as DTE in cisco.com/c/en_intl/support/docs/dial-access/…
    – jonathanjo
    Nov 30, 2018 at 16:17
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enter image description here

DATA TERMINAL EQUIPMENT(DTE)

DTE is an end instrument that converts user information into signals or reconverts received signal.These can also be called tail circuits.

DATA COMMUNICATION EQUIPMENT(DCE)

(DCE) refers to computer hardware devices used to establish, maintain and terminate communication network sessions between a data source and its destination.

DCE is connected to the data terminal equipment (DTE) and data transmission circuit (DTC) to convert transmission signals.

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