Chapter 8- Implementing VLANs & STP

802.1Q

802.1Q is the standard protocol for this tag.

• VLAN ID (most critical piece of information)

access interface

A LAN network design term that refers to a switch interface connected to end-user devices, configured so that it does not use VLAN trunking.

Data VLAN

A VLAN used by typical data devices connected to an Ethernet, like PCs and servers.

Default VLAN

A reference to the default setting of 1 (meaning VLAN ID 1) on the switchport access vlan vlan-id interface subcommand on Cisco switches, meaning that by default, a port will be assigned to VLAN 1 if acting as an access port.

Layer 3 switch

A LAN switch that can also perform Layer 3 routing functions. The name comes from the fact that this device makes forwarding decisions based on logic from multiple OSI layers (Layers 2 and 3).

Native VLAN

The one VLAN ID on any 802.1Q VLAN trunk for which the trunk forwards frames without an 802.1Q header.

Static access interface

A LAN network design term (aka access interface) but emphasizing that the port is assigned to one VLAN as a result of static configuration rather than through some dynamic process.

Trunk

In campus LANs, an Ethernet segment over which the devices add a VLAN header that identifies the VLAN in which the frame exists.

Trunk interface

A switch interface configured so that it operates using VLAN trunking (either 802.1Q or ISL).

Trunking administrative mode

The configured trunking setting on a Cisco switch interface, as configured with the switchport mode command.

Trunking operational mode

The current behavior of a Cisco switch interface for VLAN trunking.

Virtual LAN (VLAN)

A group of devices, connected to one or more switches, with the devices grouped into a single broadcast domain through switch configuration.

• Allow switch admins to separate the devices connected to the switches into separate VLANs without requiring separate physical switches, gaining design advantages of separating the traffic without the expense of buying additional hardware.

VLAN Trunking Protocol (VTP)

A Cisco-proprietary messaging protocol used between Cisco switches to communicate configuration information about the existence of VLANs, including the VLAN ID and VLAN name.

Voice VLAN

A VLAN defined for use by IP Phones, with the Cisco switch notifying the phone about the voice VLAN ID so that the phone can use 802.1Q frames to support traffic for the phone and the attached PC (which uses a data VLAN).

VTP transparent mode

Switches in transparent mode can configure VLANs, but they do not tell other switches about the changes, and they do not learn about VLAN changes from other switches.

• One of three VTP operational modes