Cisco Catalyst 3750 - Configuring VLAN Trunks; Trunking Overview; Displaying Vlans

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Catalyst 3750 Metro Switch Software Configuration Guide
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Chapter 10 Configuring VLANs
Displaying VLANs
Displaying VLANs
Use the show vlan privileged EXEC command to display a list of all VLANs on the switch, including
extended-range VLANs. The display includes VLAN status, ports, and configuration information. To
view normal-range VLANs in the VLAN database (1 to 1005), use the show VLAN database
configuration command (accessed by entering the vlan database privileged EXEC command). For a list
of the VLAN IDs on the switch, use the show vlan privileged EXEC command.
Table 10-3 lists the commands for monitoring VLANs.
For more details about the show command options and explanations of output fields, refer to the
command reference for this release.
Configuring VLAN Trunks
These sections describe how VLAN trunks function on the switch:
• Trunking Overview, page 10-16
• Encapsulation Types, page 10-18
• Default Layer 2 Ethernet Interface VLAN Configuration, page 10-19
• Configuring an Ethernet Interface as a Trunk Port, page 10-20
• Configuring Trunk Ports for Load Sharing, page 10-24
Trunking Overview
A trunk is a point-to-point link between one or more Ethernet switch interfaces and another networking device
such as a router or a switch. Ethernet trunks carry the traffic of multiple VLANs over a single link, and you
can extend the VLANs across an entire network.
Two trunking encapsulations are available on all Ethernet interfaces:
• Inter-Switch Link (ISL)—ISL is Cisco-proprietary trunking encapsulation.
• 802.1Q—802.1Q is industry-standard trunking encapsulation.
Figure 10-2 shows a network of switches that are connected by ISL trunks.
Table 10-3 VLAN Monitoring Commands
Command Command Mode Purpose
show VLAN database
configuration
Display status of VLANs in the VLAN database.
show current [vlan-id] VLAN database
configuration
Display status of all or the specified VLAN in the
VLAN database.
show interfaces [vlan
vlan-id]
Privileged EXEC Display characteristics for all interfaces or for
the specified VLAN configured on the switch.
show vlan [id vlan-id] Privileged EXEC Display parameters for all VLANs or the
specified VLAN on the switch.