[pezezin]

> 10G/2.5G/1G/100 Ethernet are all backwards compatible

Not always. The physical layers are incredibly different, and while it is true that most 1G devices also support 10M/100M, we found the hard way that some 10G switches and NICs don't.

[willis936]

10G no, but all 1000BASE-T NICs require autonegotiation for 10/100/1000 to be compliant.

[Jaruzel]

NICs maybe, but there's a whole heap of cheap home switches and hubs that don't support 10BaseT. I know this from experience.

[Sebb767]

I've also experienced some quite expensive Juniper DC switches not supporting anything below 1Gbit. Fun times.

[dicknuckle]

Some ISP core stuff too.