[CentOS] hosts fail to negotiate 1000Mbps speed

>> IIRC, one does not need a crossover cable to connect between two gigabit
>> capable hosts.

Agreed I think gigabit ethernet adapters _have_ to be autosensing of MDI 
(normal) or MDI-X (crossover) to be considered gigabit capable (ie within 
specifications).  I expect the crossover adapter may be causing enough 
interference to stop 1gbit from working thus resulting in merely 100 
mbits.

Furthermore it is entirely possible that it's a 100mbit only crossover 
adapter: it might not be crossing all 8 lines since gigabit uses 8 
lines and not 4 like 100mbit...

Cheers,
MaZe.