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Teaming of Network Interface Cards
Teaming of Network Interface Cards, or NIC Teaming, can cause instability in the networks. Such setups can
introduce disruptions to the Spanning tree and can make it undergo frequent recomputations. If intermittent
loss of connectivity to NIC teamed servers occurs for devices or hosts in the same VLAN, try to disable NIC
teaming. If the connectivity stabilizes, refer to the NIC vendor documentation in order to tune the NIC
teaming configuration.
Additional Troubleshooting for 1000BASE−X NICs
Gigabit Autonegotiation (No Link to Connected Device)
Gigabit Ethernet has an autonegotiation procedure that is more extensive than what is used for 10/100 Mbps
Ethernet (Gigabit autonegotiation specification IEEE 802.3z−1998). The Gigabit autonegotiation negotiates
flow control, duplex mode, and remote fault information. You must either enable or disable link negotiation
on both ends of the link. Both ends of the link must be set to the same value or the link does not connect.
If either device does not support Gigabit autonegotiation, disable Gigabit autonegotiation in order to force the
link up. The default configuration of all Cisco switches is autonegotiation−enabled. If you disable
autonegotiation, it hides link drops and other physical layer problems. Only disable autonegotiation to
end−devices, such as older Gigabit NICs that do not support Gigabit autonegotiation. Do not disable
autonegotiation between switches unless absolutely required, as physical layer problems can go undetected
and result in spanning tree loops. Rather than disable autonegotiation, you can contact the vendor for a
software or hardware upgrade for IEEE 802.3z Gigabit autonegotiation support.
Table 6Gigabit Autonegotiation Configuration Table
Autonegotiation
Setting
NIC Gigabit
Autonegotiation
Setting
Switch Port
Gigabit Link
Alternate
Switch
Link/NIC Link
Enabled
Enabled Up Up
Disabled
Disabled Up Up
Enabled
Disabled Down Up
Disabled
Enabled Up Down
Issue these commands for Gigabit autonegotiation configuration:
CatOS command:
set port negotiation mod/port enable | disable
•
Cisco IOS Software command:
negotiation auto no negotiation auto
•
Verifying GBIC
When you troubleshoot link issues on Gigabit Ethernet, it is also important to verify the use of the correct
Gigabit Interface Converter (GBIC) adapter with the correct cable distance. Refer to Gigabit Interface
Converter Installation Note for information on distances and cable specifications required for different
versions of GBIC adapters.