IBM 8275-416, User Manual, Page: 134 / 156

The membership of VLAN 1 is restricted to ports 1, 2, 3, 4, and 5 of Switch A;
membership of VLAN 2 is restricted to ports 4, 5, 6, 7, and 8 of Switch B while
VLAN 3 spans both switches containing ports 6, 7, and 8 of Switch A and 1, 2, and
3 of Switch B.
In this simple example, each of these VLANs can be seen as a broadcast
domain —physical LAN segments that are not constrained by their physical location.
VLANs and the switch
The switch supports VLANs that conform to the IEEE 802.1Q VLAN standard. This
specifies a standard VLAN implementation that allows operation of VLANs across a
multivendor network. This provides the services of traditional port-based VLANs, but
also allows true interoperability with other devices that support the 802.1Q standard.
In addition, the switch supports GVRP, a protocol that automates the registration of
VLANs across networks.
The switch supports up to 32 user-configured VLANs (including the Default VLAN
(VLAN 1)). A port may belong to multiple VLANs. This is useful if devices on a LAN
segment belong to multiple VLANs.
Priority and traffic classes
The switch assigns a priority of “0” to untagged frames. Otherwise, the priority
specified in the VLAN tag of the frame at the originating end-station is used to
determine which of two priority queues is used for frame transmission. Frames with
a priority of 0 to 3 are transmitted as low priority. Frames with a priority of 4 to 7 are
transmitted at high priority. The mapping from user priority to traffic class is defined
in table 7-2 of the IEEE P802.1D standard
Figure 75. An Example of VLANs
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8275-416 User’s Guide