Cisco 1710 Specifications download pdf (Page 55)

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Cisco 1710 Security Router Software Configuration Guide

78-12696-01

Chapter 3 Overview of Routing Between Virtual LANs

Why Implement VLANs?

The VLAN ID allows VLAN switches and routers to selectively forward packets

to ports with the same VLAN ID. The switch that receives the frame from the

source station inserts the VLAN ID, and the packet is switched onto the shared

backbone network. When the frame exits the switched LAN, a switch strips the

header and forwards the frame to interfaces that match the VLAN color. If you are

using a Cisco network management product such as VlanDirector, you can

actually color-code the VLANs and monitor VLAN graphically.

Why Implement VLANs?

Network managers can group logically networks that span all major topologies,

including high-speed technologies such as, ATM, FDDI, and Fast Ethernet. By

creating virtual LANs, system and network administrators can control traffic

patterns and react quickly to relocations and keep up with constant changes in the

network due to moving requirements and node relocation just by changing the

VLAN member list in the router configuration. They can add, remove, or move

devices or make other changes to network configuration using software to make

the changes.

You should consider both the advantages and disadvantages of creating VLANs

when you design your network, including these issues:

• Scalability

• Performance improvements

• Security

• Network additions, moves, and changes

Communicating Between VLANs

The Cisco 1710 Security router uses the IEEE 802.1Q protocol for routing

between VLANs.

The IEEE 802.1Q protocol is used to interconnect multiple switches and routers

and for defining VLAN topologies. IEEE 802.1Q support is currently available

only for Fast Ethernet interfaces.

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Cisco 1710 Specifications Page 55