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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
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Chapter 13 Configuring Interface Characteristics
Interface Types
These sections describe the interface types:
• Port-Based VLANs, page 13-2
• Switch Ports, page 13-2
• Routed Ports, page 13-4
• Switch Virtual Interfaces, page 13-5
• EtherChannel Port Groups, page 13-6
• 10-Gigabit Ethernet Interfaces, page 13-7
• Power over Ethernet Ports, page 13-7
• Connecting Interfaces, page 13-12
Port-Based VLANs
A VLAN is a switched network that is logically segmented by function, team, or application, without
regard to the physical location of the users. For more information about VLANs, see Chapter 15,
“Configuring VLANs.” Packets received on a port are forwarded only to ports that belong to the same
VLAN as the rece iving port. Network devices in different VLANs cannot communicate with one another
without a Layer 3 device to route traffic between the VLANs.
VLAN partitions provide hard firewalls for traffic in the VLAN, and each VLAN has its own MAC
address table. A VLAN comes into existence when a local port is configured to be associated with the
VLAN, when the VLAN Trunking Protocol (VTP) learns of its existence from a neighbor on a trunk, or
when a user creates a VLAN. VLANs can be formed with ports across the stack.
To configure VLANs, use the vlan vlan-id global configuration command to enter VLAN configuration
mode. The VLAN configurations for normal-range VLANs (VLAN IDs 1 to 1005) are saved in the
VLAN database. If VTP is version 1 or 2, to configure extended-range VLANs (VLAN IDs 1006 to
4094), you must first set VTP mode to transparent. Extended-range VLANs created in transparent mode
are not added to the VLAN database but are saved in the switch running configuration. With VTP version
3, you can create extended-range VLANs in client or server mode. These VLANs are saved in the VLAN
database.
In a switch stack, the VLAN database is downloaded to all switches in a stack, and all switches in the
stack build the same VLAN database. The running configuration and the saved configuration are the
same for all switches in a stack.
Add ports to a VLAN by using the switchport interface configuration commands:
• Identify the interface.
• For a trunk port, set trunk characteristics, and, if desired, define the VLANs to which it can belong.
• For an access port, set and define the VLAN to which it belongs.
• For a tunnel port, set and define the VLAN ID for the customer-specific VLAN tag. See Chapter 19,
“Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling.”
Switch Ports
Switch ports are Layer 2-only interfaces associated with a physical port. Switch ports belong to one or
more VLANs. A switch port can be an access port, a trunk port, or a tunnel port. You can configure a port
as an access port or trunk port or let the Dynamic Trunking Protocol (DTP) operate on a per-port basis
to set the switchport mode by negotiating with the port on the other end of the link. You must manually