Cisco Systems 3750E manual Port-Based VLANs, Switch Ports, 11-2

Chapter 11 Configuring Interface Characteristics

Understanding Interface Types

•EtherChannel Port Groups, page 11-5

•10-Gigabit Ethernet Interfaces, page 11-6

•Power over Ethernet Ports, page 11-6

•Connecting Interfaces, page 11-11

•Ethernet Management Port, page 11-12

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 13, “Configuring VLANs.” Packets received on a port are forwarded only to ports that belong to the same VLAN as the receiving 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. On Catalyst 3750-E and 3750 switches, VLANs can be formed with ports across the stack.

To configure normal-range VLANs (VLAN IDs 1 to 1005), use the vlan vlan-idglobal configuration command to enter config-vlan mode or the vlan database privileged EXEC command to enter VLAN database configuration mode. The VLAN configurations for VLAN IDs 1 to 1005 are saved in the VLAN database. In a Catalyst 3750-E and 3750 switch stack, the VLAN database is downloaded to all switches in a stack, and all switches in the stack build the same VLAN database.

To configure extended-range VLANs (VLAN IDs 1006 to 4094), you must use config-vlan mode with VTP mode set to transparent. Extended-range VLANs are not added to the VLAN database. When VTP mode is transparent, the VTP and VLAN configuration is saved in the switch running configuration, and you can save it in the switch startup configuration file by entering the copy running-configstartup-configprivileged EXEC command. In a Catalyst 3750-E and 3750 switch stack, 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 17, “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 configure tunnel ports as part of an asymmetric link connected to an IEEE 802.1Q trunk port. Switch ports are used for managing the physical interface and associated Layer 2 protocols and do not handle routing or bridging.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

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