3Com CoreBuilder 3500, Implementation Manual, Page: 163 / 592

Key Guidelines for Implementation 163
Key Guidelines for
Implementation
This section provides a series of guidelines to consider when you use
VLANs. The guidelines are organized as follows:
■
Network-based VLANs vs. multiple interfaces per VLAN
■
VLANs created by router port IP interfaces
■
Number of VLANs
■
General guidelines
Network-based
VLANs vs. Multiple
Interfaces per VLAN
You can either configure network-based IP VLANs (IP VLANs with unique
Layer 3 IP addresses) or you can define a single VLAN with the protocol
type IP and then define multiple IP routing interfaces for that single
protocol-based VLAN (an IP VLAN).
If you decide to convert an existing network-based VLAN to a
protocol-based VLAN that has multiple interfaces associated with it, use
the following procedure:
1
Remove one or more network-based VLANs.
2 Define an IP VLAN or a VLAN that supports IP as one of its protocols.
3 Define multiple IP interfaces (with different IP addresses) to use that IP
VLAN.
You can define up to 32 IP interfaces on the system, including IP routing
interfaces for static VLANs, router port IP VLANs, or any combination of
static VLANs and router port IP VLANs.
If you define multiple interfaces for an IP VLAN, you cannot subsequently
modify that IP VLAN to supply Layer 3 address information. If only one
routing interface is defined for the IP VLAN, then you can supply Layer 3
address information as long as it matches the Layer 3 information that is
specified for the routing interface.
If you use network-based VLANs, you are limited to defining only one IP
routing interface for that VLAN. When you define an IP routing interface
with the interface type
vlan
, the system does not allow you to select a
network-based IP VLAN that already has a routing interface defined for it.
For more information on IP routing interfaces, see Chapter 11.