Cisco Systems 17053 appendix Autonegotiation Valid Configuration

performance−related issues. The most common problems with NIC issues deal with speed and duplex configuration. Table 1 summarizes all possible settings of speed and duplex for FastEthernet NICs and switch ports.

Note: This section is only applicable for 10/100/1000 Mbps (1000BASE−T) NICs, and not 1000BASE−X NICs.

Table 1￿Autonegotiation Valid Configuration

Configuration
NIC	Configuration		Resulting
(Speed/Duplex)		Resulting NIC
	Switch		Catalyst	Comments
	(Speed/Duplex)	Speed/Duplex	Speed/Duplex	Assuming
				maximum
AUTO		1000 Mbps,	1000 Mbps,	capability of
	AUTO			Catalyst switch,
		Full−duplex	Full−duplex
				and NIC is
				1000 Mbps,
				full−duplex.
				Link is
				established, but
				the switch does
				not see any
				autonegotiation
				information
				from NIC.
1000 Mbps,				Since Catalyst
				switches
Full−duplex		1000 Mbps,	1000 Mbps,
	AUTO			support only
		Full−duplex	Full−duplex
				full−duplex
				operation with
				1000 Mbps,
				they default to
				full−duplex,
				and this
				happens only
				when operating
				at 1000 Mbps.
				Assuming
				maximum
AUTO	1000 Mbps,	1000 Mbps,	1000 Mbps,	capability of
	Full−duplex	Full−duplex	Full−duplex	NIC is 1000
				Mbps,
				full−duplex.
1000 Mbps,
Full−duplex	1000 Mbps,	1000 Mbps,	1000 Mbps,	Correct Manual
100 Mbps,	Full−duplex	Full−duplex	Full−duplex	Configuration
				Neither side
Full−duplex	1000 Mbps,	No Link	No Link	establishes link,
	Full−duplex			due to speed
				mismatch
	AUTO