100-490 · Question #20
Which device is a DTE device?
The correct answer is B. router. A DTE (Data Terminal Equipment) device is an end instrument that converts user information into signals or reconverts received signals. In the context of networking, a router can be considered a DTE device because it is typically at the user end of a user-network interface and…
Question
Which device is a DTE device?
Options
- ACSU/DSU
- Brouter
- Ccable modem
- DDSL modem
How the community answered
(40 responses)- A8% (3)
- B83% (33)
- C8% (3)
- D3% (1)
Explanation
A DTE (Data Terminal Equipment) device is an end instrument that converts user information into signals or reconverts received signals. In the context of networking, a router can be considered a DTE device because it is typically at the user end of a user-network interface and serves as a data source or destination. It communicates with the data circuit-terminating equipment (DCE), such as a modem, to send and receive data across the network.
Topics
Community Discussion
10
Viktor S.Jun 20, 2026Router. A router is DTE because it is the end-point equipment that generates or consumes data, sitting on the customer side of the WAN boundary, while the DCE devices (CSU/DSU, modems) are the clocking and signaling gear that connects to the carrier line.
Prof. SaraMay 25, 2026The correct answer is B, the router. In WAN connectivity, you need to separate the two sides of the serial link: the DTE side, which is your equipment generating and consuming data, and the DCE side, which provides clocking and the physical interface to the service provider. The router sits on your side of that boundary, making it the Data Terminal Equipment. The CSU/DSU, cable modem, and DSL modem in options A, C, and D are all DCE devices, because they face the carrier network and handle signal conversion and timing. A mnemonic that sticks: think DTE as "Dumb Terminal End," meaning it depends on the DCE for its clocking signal. That is exactly why on a back-to-back serial lab cable, one router gets the clock rate command applied and the other does not. The router receiving the clock is acting as DTE, and the one providing it is acting as DCE. Knowing this distinction cold will help you across the WAN and serial interface questions throughout the 100-490 blueprint.
Anjali D.Jun 26, 2026I kept second-guessing myself on this one because the CSU/DSU sits right at the edge of the LAN and I was mixing up where the demarcation point falls, but then I remembered that DTE devices are the ones that generate or use the data on the customer side of that boundary, and a router fits that definition exactly while the CSU/DSU, cable modem, and DSL modem are all DCE devices that handle clocking and signal conversion. Anyone else get tripped up by the CSU/DSU being so close to the router in a typical WAN diagram?
Luis F.Jun 28, 2026Yeah that DTE/DCE distinction clicked for me when I stopped thinking about physical location and just asked which device is providing the clock signal, because the DCE is always the one doing that, so if something is syncing timing to another device it is DCE by definition.
Imani T.May 29, 2026B, the router, is your DTE device here. DTE stands for Data Terminal Equipment, which is the end device that actually originates or receives the data, and the router fits that role perfectly on a WAN connection. The DCE side is what sits between the DTE and the physical WAN circuit and provides clocking, so your CSU/DSU, cable modem, and DSL modem all fall into that DCE bucket. The easiest way I lock this in is to remember that DCE devices are the ones that plug into the provider's line and handle signal conversion, while the router just hands data off to them. When I sat for my exam a few years back I almost second-guessed myself on a question worded almost identical to this one because they listed CSU/DSU first and my brain jumped to WAN gear equals WAN answer. I stopped, reminded myself that the CSU/DSU is the middle man doing clocking for the router, not the endpoint, and went with B. Came out of the testing center with a pass so that little pause was worth it.
Grace U.May 31, 2026Worth adding that the back-to-back serial lab scenario trips a lot of people up for exactly this reason, because when two routers are cabled directly together one interface has to be manually configured as DCE to provide the clock rate, and that tends to make the rule feel broken until you realize you are just simulating what the CSU/DSU would normally do in a real WAN setup.
Grace U.May 18, 2026B is the one you want here, and the detail that makes it stick is that a router sits on the customer side of the WAN link and relies on the DCE device, like a CSU/DSU, to provide the clocking signal, which is exactly what separates DTE from DCE in these questions.
Imani T.May 20, 2026Grace nailed the DTE/DCE split but worth adding that when you see two routers connected back-to-back in a lab with a serial cable, one router port has to be configured as DCE with the clock rate command because there is no external CSU/DSU to provide it.
Luis F.Jun 26, 2026Yep, B is right, routers are DTE devices that connect to DCE equipment like CSU/DSUs.
Viktor S.Jun 28, 2026Close enough for the exam, but worth knowing that in a back-to-back serial lab setup, one router interface acts as the DCE and supplies the clock rate, so DTE/DCE is not purely a hardware identity, it follows the cable.