Using 802.1Q Tagging - Alcatel-Lucent OmniSwitch 9900 Series Network Configuration Manual

Omniswitch aos release 8

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Configuring VLANs

Using 802.1Q Tagging

Another method for assigning ports to VLANs involves configuring a switch port or link aggregate to

process 802.1Q-tagged frames that contain a specific VLAN ID designation. This method, referred to as

802.1Q tagging (or trunking), allows a single network link to carry traffic for multiple VLANs.

The OmniSwitch implements the IEEE 802.1Q standard for sending frames through the network tagged

with VLAN identification. This section details procedures for configuring and monitoring 802.1Q tagging

on a single switch port or link aggregate group.

"Tagged" refers to four bytes of reserved space in the header of the packet. The four bytes of "tagging" are

broken down as follows: the first two bytes indicate whether the packet is an 802.1Q packet, and the next

two bytes carry the VLAN identification (VID) and priority.

When packets ingress the switch, they are classified into a VLAN based on their 802.1Q tag information.

If the packet contains an 802.1Q tag, the VLAN ID in the tag must match either the default VLAN ID

for the port or a VLAN ID for which the port is tagged. If there is no match, the packet is dropped.

If the packet is not tagged at all, the packet is placed into the default VLAN to which the port that

received the packet is assigned.

The following diagram illustrates a simple network by using tagged and untagged traffic:

Switch 1 and 2 have three VLANs, one for untagged traffic and two for tagged traffic. The ports

connecting Switch 1 and 2 are configured in such a manner that the ports accept both tagged traffic for

VLANS 2 and 3 and untagged traffic for VLAN 1.

A port can only be assigned to one untagged VLAN (in every case, this is the default VLAN

configuration). In this example the default VLAN for port 2/1 and port 4/3 is VLAN 1. The port can be

assigned to as many 802.1Q-tagged VLANs as necessary.

Configuring 802.1Q Tagging

To set a port to be a tagged port, use the

identification (VID) number and a port number. For example, to configure port 3/4 to carry traffic for

VLAN 5, enter the following command at the CLI prompt:

-> vlan 5 members port 4/3 tagged

OmniSwitch AOS Release 8 Network Configuration Guide

Tagged and Untagged Traffic Network

vlan members tagged

command and specify a VLAN

December 2017

Assigning Ports to VLANs

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