Asante Technologies 9000 manual Vlan Specifications for the IntraChassis

Advanced Management

group presents to the user a picture of connection to a single LAN, it is different from a LAN in the sense that it localizes the broadcast, multicast, and flooded traffic to parts of LAN segments, rather than to the whole LAN. In essence, a VLAN segment/group can be considered the Layer-2 broadcast segment equivalent of a Layer-3 network.

The real need for VLANs in traditional Layer-2 bridges and switches arises from their use of a basic flooding mechanism which results in unnecessary flooding traffic (broadcast, multicast, and unknown destination traffic) that causes clogging and band-width wastage in a LAN. As today’s networks expand rapidly, the Layer-2 flooding problem can become a bottleneck.

The present-day technology provides various means of controlling these flooding traffic problems, which mainly include deployment of Layer-3 devices that provide broadcast firewalls. Other methods include IP multicast control, customized packet filtering, etc. It is evident that these solutions press the requirement for Layer-3 routers. As all of us know, more and more deployment of legacy routers increases the latency of traffic forwarding and eventually degrades network performance. Also, the cost of maintenance increases and configuration becomes more complex with more Layer-3 devices.

In contrast, VLAN technology offers a simple and efficient solution that enhances the network performance, bandwidth utilization, and more importantly, network security, by localizing the broadcast, multicast, and unicast flooding traffic.

Port based VLANs provide one of the many VLAN approaches that solve the problem of unnecessary flooding. They allow ports to be grouped in VLAN segments, so as to limit the transmission of incoming broadcast, multicast, and unknown destination address frames in a VLAN segment to only those ports that are grouped in that segment. This grouping produces selective flooding, rather than flooding to all ports in the system. This, in turn, greatly reduces the unnecessary flooding traffic in a network.

Other VLAN approaches include MAC-based VLANs and policy-based VLANs. The present version of the IntraChassis 9000 supports port-based VLANs in compliance with IEEE P802.1Q/Draft 8 standards. The following sections of the chapter describe the concepts and details needed to configure and manage VLANs on Intrachassis switches.

VLAN Specifications for the IntraChassis 9000

The present IntraChassis 9000 supports the following IEE P802.1Q features:

Page 5-12