100-490 · Question #13
Which two pins does an RJ-45 connector use to transmit data? (Choose two.)
The correct answer is A. 1 B. 2. You've hit your Sonnet limit · resets Jun 8, 9am (UTC)
Question
Which two pins does an RJ-45 connector use to transmit data? (Choose two.)
Options
- A1
- B2
- C3
- D4
- E6
How the community answered
(39 responses)- A87% (34)
- C3% (1)
- D8% (3)
- E3% (1)
Explanation
You've hit your Sonnet limit · resets Jun 8, 9am (UTC)
Topics
Community Discussion
7
Dervla O.May 31, 2026Pins 1 and 2 are correct. In standard 10/100 Ethernet wiring (T568A or T568B), the transmit pair sits on pins 1 and 2, which is why every other option here is a distractor, pins 3 and 6 handle receive, and 4 and 5 are unused in that context.
Carlos M.May 31, 2026Solid breakdown, though worth noting that pins 4 and 5 being "unused" only holds for 10/100, since 1000BASE-T puts all four pairs to work including 4-5 and 7-8.
Carlos M.Jun 7, 2026Pins 1 and 2 are TX+ and TX-, right, so what pairs with them to receive?
Orla P.May 20, 2026Pins 1 and 2 are your TX pair on a standard 10/100 Ethernet port, so A and B are the ones the exam is looking for. Quick follow-up though: when you get to a question like this on test day, are you thinking about it from the T568B wiring standard angle, or are you approaching it more from the NIC perspective where TX on one end becomes RX on the other?
Dervla O.May 22, 2026The TX/RX flip is worth knowing cold, but on test day the faster move is to recognize what the question is actually testing, which is usually cable type selection or troubleshooting, not pin memorization, so anchor your recall to that function rather than the wiring diagram.
Toby R.Jun 13, 2026Pins 1 and 2, full stop. In a standard 10/100 Ethernet setup using T568B, pins 1 and 2 carry the transmit pair (TX+ and TX-), while pins 3 and 6 handle the receive side. The gotcha here is that 3 and 6 look tempting if you are half-remembering that they are part of the active pairs, which they are, just on the receive end, not transmit. I almost second-guessed myself on this one because the question just says "transmit data" without specifying direction from the NIC's perspective, but Cisco means the host-to-switch direction, so 1 and 2 is what they want.
Dervla O.Jun 14, 2026The direction framing is the real trap on those questions, so it is worth drilling that the TX pair from the NIC perspective becomes the RX pair at the switch, which is exactly why a straight-through cable works without any manual crossover.