3Com CoreBuilder 3500, Implementation Manual, Page: 178 / 592

178 C
HAPTER
9: V
IRTUAL
LAN
S
Trunking with the
default VLAN
removed
If you remove the default VLAN, the system has nowhere to return ports
altered by trunking, as discussed in these examples:
■
If you have VLANs (but no default VLAN) and you then define a trunk
for ports in one of the VLANs, those ports are removed from that
VLAN and are not assigned to any other VLAN. If you later remove the
trunk, these ports are not reassigned to the VLAN; they no longer
have a VLAN associated with them. For example:
■
If you have VLANs (but no default VLAN) and you modify an existing
trunk that has ports in one VLAN, any port that is removed from the
trunk is removed from the VLAN and no longer has a VLAN. For
example:
See Chapter 8 for information on using trunks.
Static Port-based
VLANs
You can explicitly configure port-based VLAN interfaces instead of relying
on GVRP to dynamically create port-based VLAN interfaces.
Important Considerations
When you create this type of VLAN interface, review these guidelines:
■
When you select the bridge ports that you want to be part of the
VLAN, the bridge ports that you specify as part of the VLAN are the
same as your physical ports, unless you have created trunks or unless
you have DAS ports defined on an FDDI module.
■
If you define trunks, a single bridge port called the anchor port (the
lowest-numbered port in the trunk) represents all ports that are part
of the trunk. Only the anchor bridge port for the trunk, not the other
bridge ports in the trunk, is selectable when you are creating VLANs.
For more information, see Chapter 8.
Ports Before Action Trunking Action Ports After Action
ipvlan1: ports 1-11 Define trunk with
ports 5-8 ipvlan1: ports 1-4, 9-11
Ports Before Action Trunking Action Ports After Action
ipvlan1: ports 1-11 (ports
5-8 are trunk ports) Modify existing trunk
to have ports 6-8
(remove port 5, the
anchor port) ipvlan1: ports 1-4, 6-11 (port
6 is new anchor port)