Number Of Vlans - 3Com corebuilder 3500 Implementation Manual

Number of VLANs

Your system supports a maximum of 64 VLANs based on a physical limit
of 125 VLAN table entries. To determine the number of VLANs of any
type that you can have on the system, use the following equation:
Number of VLANs supported =
(125 divided by the number of protocol suites) minus 3
Important Considerations
When you use the VLAN equation to calculate the number of VLANs
that you can have on your system, keep in mind that the equation
provides an estimate. Your system may allow additional or fewer
VLANs, depending on your configuration, use of protocol suites, and
chosen tag style. If, for example, you are using the Release 3.0 VLAN
tag style of all ports, this formula generally yields a maximum number
of VLANs. If you use the Release 1.2 tag style of taggedVlanPorts,
then this formula generally yields a minimum number of VLANs.
The number of allowable VLANs includes the default VLAN.
Determining the Number of Protocol Suites
To perform the calculation, first determine the total number of protocol
suites used on your system. Use the following guidelines:
IP counts as one protocol suite for IP VLANs.
AppleTalk counts as one protocol suite for AppleTalk VLANs.
Generic IPX, which uses all four IPX types, counts as four protocol
suites. (Each IPX type alone counts as one.)
DECnet counts as one protocol suite for DECnet VLANs.
The unspecified type of protocol suite counts as one for the default
VLAN or port-based VLANs. (Even if you have only the unspecified
protocol suite on the system, the limit is still 64 VLANs.)
If you are using GVRP (for dynamic port-based VLANs), use the type
unspecified in the VLAN formula
Remember to include the unspecified type for the default VLAN, even if
you have removed the default VLAN and do not have another VLAN
defined with the unspecified protocol type.
In addition to the limit on the number of VLANs, you are limited to 15
different protocols that can be implemented by the protocol suites on the
system. See Table 19 later in this chapter for a list of supported protocol
suites and the number of protocols within each suite.
Key Guidelines for Implementation 165