Chapter 7 Configuring Vlans; Understanding Vlans - Cisco ONS 15454 Software Feature And Configuration Manual

Configuring VLANs
This chapter describes VLAN configurations for the ML-Series card. It describes how to configure IEEE
802.1Q VLAN encapsulation. For more information about the Cisco Internet Operating System (IOS)
commands used in this chapter, refer to the Cisco IOS Command Reference publication.
This chapter contains the following major sections:
•
•
•
•
Configuring VLANs is optional. Complete general interface configurations before proceeding with
Note
configuring VLANs as an optional step.

Understanding VLANs

VLANs or bridge groups enable network managers to group users logically rather than by physical
location. A VLAN is an emulation of a standard LAN that allows secure intra-group data transfer and
communication to occur without the traditional restraints placed on the network. It can also be
considered a broadcast domain set up within a switch. With VLANs, switches can support more than one
subnet (or VLAN) on each switch and give routers and switches the opportunity to support multiple
subnets on a single physical link. A group of devices that belong to the same VLAN, but are part of
different LAN segments, are configured to communicate as if they were part of the same LAN segment.
VLANs enable efficient traffic separation and provide excellent bandwidth utilization. VLANs also
alleviate scaling issues by logically segmenting the physical LAN structure into different subnetworks
so that packets are switched only between ports within the same VLAN. This can be very useful for
security, broadcast containment, and accounting.
ML-Series software supports port-based VLANs and VLAN trunk ports, which are ports that carry the
traffic of multiple VLANs. Each frame transmitted on a trunk link is tagged as belonging to only one
VLAN.
ML-Series software supports VLAN frame encapsulation through the IEEE 802.1Q standard on both the
ML100T-12 and the ML1000-2. The Cisco ISL VLAN frame encapsulation is not supported. ISL frames
will be broadcast at Layer 2, or dropped at Layer 3.
Cisco ONS 15454 SONET/SDH ML-Series Multilayer Ethernet Card Software Feature and Configuration Guide, R4.0
78-15224-02
Understanding VLANs, page 7-1
Configuring IEEE 802.1Q VLAN Encapsulation, page 7-2
IEEE 802.1Q VLAN Configuration Example, page 7-3
Monitoring and Verifying VLAN Operation, page 7-5
C H A P T E R
7
7-1