3Com 4007, Implementation Manual, Page: 282 / 684

282 C
HAPTER
14: V
IRTUAL
LAN
S
(VLAN
S
)
Your Multilayer Switching Modules impose two important limits
regarding the number of VLANs and the number of protocols:
■
Number of VLANs supported — To determine the minimum
number of VLANs that the Multilayer Switching Module can support,
use the equation described in “Number of VLANs” earlier in this
chapter. A Multilayer Switching Module supports a maximum of 64
VLANs.
■
Maximum number of protocols — Use the value 15 as the limit of
protocols that can be implemented on the Multilayer Switching
Module. A protocol suite that is used in more than one VLAN is
counted only once towards the maximum number of protocols. For
example, the DECnet protocol suite uses 5 of the available 15
protocols, regardless of the number of VLANs that use DECnet.
Establishing Routing
Between VLANs
Your Multilayer Switching Modules support routing using IP, IPX, and
AppleTalk VLANs. If VLANs are configured for other routable network
layer protocols, they can communicate between them only via an external
router or a Multilayer Switching Module configured for routing.
The Multilayer Switching Module’s routing over bridging model lets you
configure routing protocol interfaces based on a static VLAN defined for
one or more protocols. You must first define a VLAN to support one or
more protocols and then assign a routing interface for each protocol
associated with the VLAN. (You can also opt to use a routing versus
bridging model by defining a router port IP interface, as defined in
Chapter 16).
Because the Multilayer Switching Modules support router port IP
interfaces as well as IP router interfaces for static VLANs, you must now
specify the interface type
vlan
when you define an IP interface for a
static VLAN.
Important Considerations
To create an IP interface that can route through a static VLAN, you must:
1
Create a protocol-based IP VLAN for a group of bridge ports. (If the VLAN
overlaps with another VLAN on any ports, be sure that you define it in
accordance with the requirements of your VLAN mode.)
(This IP VLAN does not need to contain Layer 3 information unless you
want a network-based IP VLAN. See “Network-based IP VLANs” later in
this chapter.)