Cisco FAN-MOD-6HS= Datasheet download pdf (Page 321)

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Release Notes for Cisco IOS Release 12.1E on the Catalyst 6500 and Cisco 7600 Supervisor Engine and MSFC

OL-2310-11

Troubleshooting

Module Troubleshooting

This section contains troubleshooting guidelines for module problems:

• When you hot insert a module into a chassis, be sure to use the ejector levers on the front of the

module to seat the backplane pins properly. Inserting a module without using the ejector levers

might cause the supervisor engine to display incorrect messages about the module. For module

installation instructions, refer to the Catalyst 6500 Series Module Installation Guide.

• Whenever you connect an interface that has duplex set to autonegotiate to an end station or another

networking device, make sure that the other device is configured for autonegotiation as well. If the

other device is not set to autonegotiate, the autonegotiating port will remain in half-duplex mode,

which can cause a duplex mismatch resulting in packet loss, late collisions, and line errors on the

link.

VLAN Troubleshooting

Note Catalyst 6500 series switches do not support ISL-encapsulated Token Ring frames. To support trunked

Token Ring traffic in your network, make trunk connections directly between switches that support

ISL-encapsulated Token Ring frames. When a Catalyst 6500 series switch is configured as a VTP server,

you can configure Token Ring VLANs from the switch.

Although DTP is a point-to-point protocol, some internetworking devices might forward DTP frames.

To avoid connectivity problems that might be caused by a switch acting on these forwarded DTP frames,

do the following:

• For interfaces connected to devices that do not support DTP, in which trunking is not currently being

used, configure interfaces with the switchport mode access command, which puts the interface into

access mode and sends no DTP frames.

• When manually enabling trunking on a link to devices that do not support DTP, use the switchport

nonegotiate and switchport mode trunk commands, which puts the interface into trunking mode

without sending DTP frames.

Spanning Tree Troubleshooting

The Spanning Tree Protocol (STP) blocks certain ports to prevent physical loops in a redundant

topology. On a blocked port, switches receive spanning tree bridge protocol data units (BPDUs)

periodically from neighboring switches. You can configure the frequency with which BPDUs are

received by entering the spanning-tree vlan vlan_ID hello-time command (the default frequency is set

to 2 seconds). If a switch does not receive a BPDU in the time period defined by the spanning-tree vlan

vlan_ID max-age command (20 seconds by default), the blocked port transitions to the listening state,

the learning state, and to the forwarding state. As it transitions, the switch waits for the time period

specified by the spanning-tree vlan vlan_ID forward-time command (15 seconds by default) in each

of these intermediate states. If a blocked spanning tree interface does not receive BPDUs from its

neighbor within 50 seconds, it moves into the forwarding state.

Note We do not recommend using the UplinkFast feature on switches with more than 20 active VLANs. The

convergence time might be unacceptably long with more than 20 active VLANs.

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Cisco FAN-MOD-6HS= Datasheet Page 321