Leaflet

OL-11615-01

This example shows how to disable auto-negotiation on port 2 on module 1:

Console> (enable)#set trunk 1/2 off

Port(s) 1/2 trunk mode set to off.

Console> (enable)

For more information on the set trunk command on the Catalyst 6500, refer to the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_8_5/cmd_ref/setsy

_tr.htm#wp1170006

For more information on the set trunk command on the Catalyst 4500, refer to the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat4000/8_3/command/set_s_z.htm#wp1025473

To disable auto-negotiated trunking in Cisco IOS software, use the switchport mode access command.

Setting the port mode to access makes the port a nontrunking, nontagged single VLAN Layer 2 interface:

Switch(config-if)# switchport mode {access | trunk | {dynamic {auto | desirable}} |

dot1q-tunnel}

This example shows how to set a port as nontrunking, nontagged single-VLAN Layer 2:

Switch(config)# interface

type slot/port

Switch(config-if)# switchport mode access

Switch(config-if)#

Note Catalyst 6500 switches running Cisco IOS software support the switchport host macro command. The

switchport host macro command was designed to expedite the configuration of switch ports that

connect to end stations. Using the switchport host macro command sets the switch port mode to access,

enables spanning tree PortFast, and disables channel grouping, all at the same time. The switchport host

macro command can be used as an alternative to the switchport mode access command.

For more information on the switchport mode access command on the Catalyst 6500, refer to the

following URL:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/cmdref/s1.htm#wp1022676

For more information on the switchport mode access command on the Catalyst 4500, refer to the

following URL:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat4000/12_2_31s/cmdref/snmp

_vtp.htm#wp1210450

Per VLAN Spanning Tree (PVST)

Per-VLAN Spanning Tree (PVST) is an available feature on Catalyst 6500 and 4500 Series switches that

implements a separate instance of spanning tree for each VLAN configured in the network. PVST is

available on switches running Cisco IOS and Catalyst OS software, and it is enabled by default. It is

recommended to leave PVST always enabled. Having a separate instance of STP per VLAN makes the

network more resilient to attacks against spanning tree. If a problem occurs in one VLAN, the effects

are contained in that VLAN, shielding the rest of the network.

There are different versions of PVST that all maintain separate spanning tree instances per VLAN, and

work in a similar fashion. Per VLAN Spanning Tree (PVST) is the original version, which uses ISL

trunking. Per VLAN Spanning Tree Plus (PVST+) provides the same functionality as PVST using

802.1Q trunking technology rather than ISL. PVST+ is an enhancement to the 802.1Q specification and