Installation guide

Release Notes for Catalyst5000 Family Software Release4.x

OL-2306-01

Usage Guidelines, Restrictions, and Troubleshooting

VTP, VLANs, and VLAN Trunks

This section contains usage guidelines, restrictions, and troubleshooting information that apply to VTP,

VLANs, and VLAN trunks.

• Although the Dynamic Trunk Protocol (DTP) is a point-to-point protocol, some internetworking

devices might forward DTP frames. To avoid connectivity problems, follow these guidelines:

–

For ports connected to non-Catalyst family devices in which trunking is not being used,

configure trunk-capable Catalyst5000 family switch ports to off by entering the set trunk

mod_num/port_num off command.

–

When trunking to a Cisco router, use the set trunk mod_num/port_num nonegotiate command.

The nonegotiate keyword transitions a link into trunking mode without sending DTP frames.

• With Cisco IOS software release 12.0, the Catalyst8510 campus switch router (CSR) does not

process untagged packets (packets on the native VLAN) received on an IEEE802.1Q trunked

interface (all such packets are dropped). If you configure Catalyst8510 CSR subinterfaces to trunk

using 802.1Q encapsulation, traffic cannot be carried successfully on the native VLAN for the trunk

configured on the Catalyst5000 family switch.

Workaround: Create an unused VLAN and assign that VLAN as the native VLAN for the 802.1Q

trunk on the Catalyst5000 family switch. Verify the native VLAN assignment for the trunk using

the show trunk command.

This problem is tracked as a defect against the Catalyst8510 CSR software (CSCdk77676).

EtherChannel

This section contains usage guidelines, restrictions, and troubleshooting information that apply to Fast

and Gigabit EtherChannel.

• When using Fast EtherChannel, if a “SPANTREE-2: Channel misconfig - x/x-x will be disabled” or

similar syslog message is displayed, it indicates a mismatch of Fast EtherChannel modes on the

connected ports. We recommend that you correct the configuration and reenable the ports by

entering the set port enable command. Valid EtherChannel configurations include:

• If you are using media-independent interface (MII) connectors, Fast EtherChannel does not work on

the 100BASE-TX, RJ-45 supervisor engine (WS-X5509).

• With a large number of channels, trunks, or VLANs, or a change of channel configuration (for

example, off to auto), or upon Fast EtherChannel module reboot, ports might take up to five minutes

to form a channel and to participate in spanning tree. (During this interval, the port does not appear

in show spantree command output.) If it takes more than ten minutes for a channel to form and

appear on spanning tree, disable and reenable the ports. In addition, it might take up to two minutes

to unbundle a channel after changing the channel mode.

Port Channel Mode Valid Neighbor Port Channel Mode(s)

desirable desirable or auto

auto desirable or auto

1. If both the local and neighbor ports are in auto mode, an EtherChannel bundle will not form.

on on

off off