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According to Wikipedia about link pulse, link pulse is used to detect link failure/L1 status. Autonegotiation on FE and GE use link pulse mechanism.

When speed and duplex are forced and autonegotiation is turned off, is the interface still generate link pulse?

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I believe the answer is no.

Unfortunately, because of the history of Ethernet, you often see statements about it that are only true for 10Mb/s operation, or only for half-duplex operation and so forth.

802.3 clause 28.1.4.1 says:

Auto-Negotiation does not support the transmission of the NLP sequence. The 10BASE-T PMA provides this function if it is connected to the MDI.

In other words, you don't get link test pulses sent if you force the speed to 100Mb/s or 1000Mb/s. They are unnecessary, because idle symbols are continuously transmitted in these modes.

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  • Then how link status is determined up or down when speed and duplex are forced?
    – Ron Vince
    Sep 28 '14 at 3:09
  • 100BASE-TX and above use a more sophisticated encoding than 10BASE-T which include 'special' symbols. Between frames, the transmitter is continually sending idle symbols. When the receiver has started to the decode these, it'll bring the link up.
    – richardb
    Sep 28 '14 at 8:37

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