3Com 7600 manual 12-18CHAPTER 12 ATM, LAN EMULATION, and Virtual Lans

12-18CHAPTER 12: ATM, LAN EMULATION, AND VIRTUAL LANS

ability to define multiple emulated LANs permits the network manager to create several bridged LAN domains within a single ATM network.

vLANs create secure workgroups, erect firewalls against broadcast storms and allow networks to be reconfigured - all without changing cabling or adding equipment. Network administrators can implement additions, moves, and changes simply by redefining groups in the network management system and remotely configuring parameters in the end device or ATM switch.

In addition, vLANs can extend the life of routers in the network. Since traffic is switched within the vLAN at full rate, routers need only deal with the traffic between the vLANs, cutting down on the routed traffic load.

Since traffic is switched within vLANs at full rate regardless of protocol, you can configure the LAN in a variety of ways without inhibiting performance. This leaves your routers free to route traffic across the virtual LAN boundaries and into the WAN.

Virtual LANs in the A vLAN brings together logically related, but not necessarily physically

7600 Cardconnected, Ethernet segments on the ATM network into a common high-bandwidth broadcast domain. A vAN is defined simply as an Emulated LAN together with all segments attached to it and the stations connected to these segments. Multiple vLANs can operate independently on a single ATM network; each vLAN corresponds to a distinct ELAN.

Connecting Local A vLAN will usually contain some Ethernet segments physically connected Segments to a vLAN to the 7600 Card (local segments) as well as remote segments located in different parts of the ATM network. Logically, the connection of the local

Ethernet segments into a vLAN proceeds in two steps: first, they are formed into a local bridged-LAN environment by connecting them to a local bridge (see “Bridged-LAN Environments in the 7600 Card” on page 11-11) and then the local bridged-LAN environment is connected to remote bridged-LAN environments in the same vLAN by connecting the bridge to the Emulated LAN.

The 7600 Card bridge setup handles both of these steps. Local Ethernet segments are attached one-by-one to the appropriate bridge by simple menu actions. Then an ATM connection is requested, causing the bridge to be connected into an Emulated LAN. As a result, when the bridge setup is completed, the local bridged-LAN environment is already part of