Virtual Lans (Vlans) - HP J3100B Installation And Configuration Manual

Advanced Concepts

Virtual LANs (VLANs)

Virtual LANs (VLANs)
The switch supports port-based virtual LANs (VLANs). A VLAN is a collection
of ports that belong to a single broadcast domain. (That is, all ports carrying
traffic for a particular subnet address would belong to the same VLAN.) This
allows workgroups to be defined on the basis of their logical function instead
of their physical location, and does not require recabling.
Port-based VLANs are typically used to enable broadcast traffic reduction and
increased security. By using port groupings, traffic is isolated to specific
domains. A group of network users assigned to a VLAN are a separate traffic
domain so that packets are forwarded only between ports that are designated
for the same VLAN. Cross-domain broadcast traffic is eliminated and band-
width is saved by not allowing packets to flood throughout the network.
For example, if ports 1 through 5 belong to VLAN_1 and ports 6 through 10
belong to VLAN_2, traffic from end-node stations on ports 2 through 5 is
restricted to only VLAN 1, while traffic from ports 6 through 9 is restricted to
only VLAN 2. For nodes on VLAN_1 to communicate with VLAN_2, their traffic
must go through an external router via ports 1 and 10.
Figure 7-8. Example of Routing Between VLANs via an External Router
7-14
External
Router
Switch with Two
VLANs Configured
Port 2
VLAN_1
Port 3
Port 4
Port 1
Port 5
Port 6
Port 10
Port 7
Port 8
Port 9
VLAN_2