100BASE-TX signal received by 10BASE-TX port

Nov 29, 2005 2 Replies

Hi, I have an interesting question for you all.



When two 10/100 Ethernet devices are configured statically, but differently configured, say, one device port is configured to 10M, while the other device port is configured to



100M. And the two wronfully configured ports are connected with a copper cable.

In this situation, the 10M device port looks working ok, while the 100M device port looks 'link down'. My question is why the 10M device port looks working ok (link-up).



The 10M device company claims the following statement;


I found the following information in IEEE 802.3 by myself. Just FYI.

A 10baseT device signals link up when it sees link pulses. While there are specific timing specs for link pulses, the detector may accept a wider range than the specification. If the 100baseT signal looks enough like link pulses, it might believe it. This would be more likely for devices designed before 100baseTX.

-- glen

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