Troubleshooting Guide

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.
Cisco Catalyst Switch Compatibility and Operation-Specific Issues
These sections deal with specific Cisco Catalyst switch issues that can affect performance, compatibility,
and interoperation of certain NICs.
Catalyst 8510 and 8540 CSR
In the campus switch router (CSR) Cisco IOS Software Release 12.0(5)W5(13), autonegotiation for speed
and duplex are enabled by default. In earlier releases, autonegotiation is not supported by default. As a
result, each connected interface must be set to run in full-duplex mode. If you upgrade to Cisco IOS
Software Release 12.0(5)W5(13) with a router that runs in manually full-duplex mode, you experience
performance issues. The symptoms include high collision rate, reduced throughput, and more packet
drops. This is because the Catalyst 8500 waits to autonegotiate with the connected device. Now that the
connected device is forced to run in full-duplex mode, it does not participate in autonegotiation. Based on
the specification, this causes the Catalyst 8500 interface to settle in half-duplex mode, which causes a
mismatch between the device and the Catalyst 8500 at the interface level. Catalyst 8500 interface defaults
to half-duplex mode when the peer is incapable of negotiation.
Catalyst 6000 and 6500 Switches
This table describes Cisco bug IDs found on the Catalyst 6000 and 6500 switches.
Table 7
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
Cisco Bug ID
Resolved
In
Description
CSCdm48887
(registered
customers
only)
5.2.3,
5.3.1a
When a port goes into the
errdisable state on a
Catalyst 6000 or 6500, the
switch inadvertently learns the
MAC addresses of other
devices to be learned from the
errdisable port. The
errdisable state is caused by
excessive late collisions on a
port. Since all traffic on that
VLAN is forwarded incorrectly
out of the incorrect port, there is
a loss of connectivity. This
errdisable state can appear
as a result of a duplex mismatch
or faulty NIC.
When a Gigabit connection is
reset on a Catalyst 6000 or