3Com 4007, Implementation Manual, Page: 252 / 684

252 C
HAPTER
14: V
IRTUAL
LAN
S
(VLAN
S
)
VLANs Created by
Router Port IP
Interfaces
By default, the Multilayer Switching Modules use a routing over bridging
model, in which any frame is bridged before it is potentially routed. If you
want to define IP routing interfaces that use a routing versus bridging
model, however, you can bypass your static VLAN configuration and
instead go directly to defining an IP interface on a single router port (a
router port IP interface).
If you define a router port IP interface, note the following information:
■
Defining an IP interface for a router port requires the interface type
port. Defining an IP interface for a configured IP VLAN requires you to
specify the interface type of vlan.
■
The IP interface definition procedure for a router port requires that you
place the Multilayer Switching Module in allClosed mode. The
allClosed mode prevents MAC addresses from being shared between
the router port IP VLAN and any other VLANs and enables the router
port to ignore Spanning Tree states on the port.
■
After you define the router port IP interface and change the VLAN
mode to allClosed, the following events occur:
■
The Multilayer Switching Module deletes all other VLANs and
redefines the default VLAN. You must redefine any VLANs that you
had configured, keeping in mind that unicast traffic will no longer
be forwarded between VLANs. You must define routing interfaces
to allow forwarding between VLANs. Also, you cannot specify the
bridge port owned by the router port IP interface in any VLAN that
you configure or modify.
■
The Multilayer Switching Module creates a special protocol-based
VLAN called a router port IP VLAN and assigns to it the next
available VID. The VLAN displays identify the origin of a router port
IP VLAN as router, as well as the port that is owned by the router
port IP interface. You cannot modify or remove a router port IP
VLAN, nor can you change its Ignore STP mode (which is always
enabled).
■
To disable bridging entirely for the router port, remove that port from
the default VLAN.
For more information about defining a router port IP interface on a
Multilayer Switching Module, see Chapter 16.