IBM 12.1(22)EA6 - Manual (Page 232)

12-2
Cisco Systems Intelligent Gigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
24R9746
Chapter 12 Configuring VLANs
Understanding VLANs
Figure 12-1 shows an example of VLANs segmented into logically defined networks.
Figure 12-1 VLANs as Logically Defined Networks
VLANs are often associated with IP subnetworks. For example, all the end stations in a particular IP
subnet belong to the same VLAN. Interface VLAN membership on the switch is assigned manually on
an interface-by-interface basis. When you assign switch interfaces to VLANs by using this method, it is
known as interface-based, or static, VLAN membership.
Supported VLANs
The switches support 250 VLANs. VLANs are identified with a number from 1 to 4094. VLAN IDs 1002
through 1005 are reserved for Token Ring and FDDI VLANs. VTP only learns normal-range VLANs,
with VLAN IDs 1 to 1005; VLAN IDs greater than 1005 are extended-range VLANs and are not stored
in the VLAN database. The switch must be in VTP transparent mode when you create VLAN IDs from
1006 to 4094.
The switch supports per-VLAN spanning-tree plus (PVST+) and rapid PVST+ with a maximum of 64
spanning-tree instances. One spanning-tree instance is allowed per VLAN. See the
“Normal-Range
VLAN Configuration Guidelines” section on page 12-5 for more information about the number of
spanning-tree instances and the number of VLANs. The switch supports IEEE 802.1Q trunking for
sending VLAN traffic over Ethernet ports.
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