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Static Virtual LANs (VLANs)
Static VLAN Operation
Protocol VLAN Environment. Figure 2-2 can also be applied to a protocol
VLAN environment. In this case, VLANs “W” and “X” represent routable
protocol VLANs. VLANs “Y” and “Z” can be any protocol VLAN. As noted for
the discussion of multiple port-based VLANs, VLAN 1 is not shown. Enabling
internal (IP) routing on the switch allows IP traffic to move between VLANs
on the switch. However, routable, non-IP traffic always requires an external
router.
Overlapping (Tagged) VLANs
A port can be a member of more than one VLAN of the same type if the device
to which the port connects complies with the 802.1Q VLAN standard. For
example, a port connected to a central server using a network interface card
(NIC) that complies with the 802.1Q standard can be a member of multiple
VLANs, allowing members of multiple VLANs to use the server. Although these
VLANs cannot communicate with each other through the server, they can all
access the server over the same connection from the switch. Where VLANs
overlap in this way, VLAN “tags” are used in the individual packets to distin-
guish between traffic from different VLANs. A VLAN tag includes the particu-
lar VLAN I.D. (VID) of the VLAN on which the packet was generated.
Figure 2-3. Example of Overlapping VLANs Using the Same Server
Similarly, using 802.1Q-compliant switches, you can connect multiple VLANs
through a single switch-to-switch link.
ProCurve
Switch
802.1Q-Compliant
Server