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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter27 Troubleshooting
Preventing Autonegotiation Mismatches
Step 10 When prompted, assign a name to the cluster, and press Return.
The cluster name can be 1 to 31 alphanumeric characters, dashes, or underscores.
Step 11 When the initial configuration displays, verify that the addresses are correct.
Step 12 If the displayed information is correct, enter Y, and press Return.
If this information is not correct, enter N, press Return, and begin again at Step9.
Step 13 Start your browser, and enter the IP address of the new command swi tc h.
Step 14 From the Cluster menu, select Add to Cluster to display a list of candidate switches to add to the cluster.

Recovering from Lost Member Connectivity

Some configurations can prevent the command switch from maintaining contact with member switches.
If you are unable to maintain management contact with a member, and the member sw itch is forwarding
packets normally, check for these conflicts:
•A member switch (Catalyst 3550, Catalyst 3500 XL, Catalyst 2950, Catalyst 2900 XL, Catalyst
2820, and Catalyst 1900 switch) cannot connect to the com mand swi tch thro ugh a p ort that i s
defined as a network port.
•Catalyst 3500 XL, Catalyst 2950, Catalyst 2900 XL, Catalyst 2820, and Catalyst 1900 member
switches must connect to the command switch through a port that belongs to t he same management
VLAN.
•A member switch (Catalyst 3550, Catalyst 2950, Catalyst 3500 XL, Catalyst 2900 XL, Catalyst
2820, and Catalyst 1900 switch) connected to the command switch through a secured port can lose
connectivity if the port is disabled because of a securi ty viol at ion.
Preventing Autonegotiation Mismatches
The IEEE 802.3AB autonegotiation protocol manages the switch settings fo r speed (10 Mbps, 100 Mbps,
and 1000 Mbps excluding GBIC ports) and duplex (half or full ). There are situations when this protocol
can incorrectly align these settings, reducing performance. A mismatch occurs unde r these
circumstances:
•A manually-set speed or duplex parameter is different from the manually set speed or duplex
parameter on the connected port.
•A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.
To maximize switch performance and ensure a link, follow one of these guidelines when changing the
settings for duplex and speed:
•Let both ports autonegotiate both speed and duplex.
•Manually set the speed and duplex parameters for the ports on both ends of the connection.
Note If a remote device does not autonegotiate, configure the duplex settings on the two ports to match.
The speed parameter can adjust itself even if the connected port does not autonegotiate.