Default Vlan; Modifying The Default Vlan; Flooding Decisions In The Corebuilder 2500 - 3Com CoreBuilder 2500 User Manual

Default VLAN

Flooding Decisions in
the CoreBuilder 2500
When you start the CoreBuilder 2500 Extended Switching software, the
system creates a default VLAN. Initially, the default VLAN includes all the
system's switch ports. The CoreBuilder 2500 default VLAN defines:
The flood domain for protocols that are not supported by any VLAN in
the system
The flood domain for protocols that are supported by a VLAN in the
system but received on nonmember ports
Both cases represent exception flooding conditions that are described in
the following sections.

Modifying the Default VLAN

If you insert a LAN card or create an ATM LEC, new switch ports can
dynamically appear. When a new switch port that is not part of a default
VLAN appears in the system at initialization, the system software adds
that switch port to the first default VLAN defined in the system.
With CoreBuilder 2500 VLANs you can modify the initial default VLAN to
form two or more subsets of switch ports. If you remove the default
VLAN and no other VLANs are defined for the system, no flooding of
traffic can occur.
Protocol-sensitive VLANs directly affect how the CoreBuilder 2500 system
performs flooding. Without protocol-sensitive VLANs, the flooding
process forwards data to all switch ports in the system. With
protocol-sensitive VLANs, the flooding process follows this model:
When the system receives a frame that needs to be flooded, the
system decodes the frame's protocol.
If a VLAN for the frame's protocol exists in the system and the frame's
source port is a member of the VLAN, then the system floods the
frame to the ports that are assigned to that VLAN.
If a VLAN for the frame's protocol exists in the system but the frame's
source port is not a member of the VLAN, then the system floods the
frame to the default VLAN that is assigned to that port.
If there is no VLAN for the frame's protocol, then the system floods
the frame to the default VLAN for the port that received it.
About VLANs 2-5