3Com CoreBuilder 3500, Implementation Manual

Page: 169 / 592

VLAN allOpen or allClosed Mode 169
VLAN allOpen or
allClosed Mode
You can select allOpen or allClosed as the VLAN mode for your entire
system. The default is allOpen.
3Com’s use of the term “allOpen” is equivalent to the IEEE Standard
802.1Q term “Shared VLAN Learning” (SVL). The term “allClosed” is
equivalent to the IEEE 802.1Q term “Independent VLAN Learning” (IVL).
3Com imposes the restriction that you must choose one VLAN mode for
the entire system. More complex logic for assigning SVL and IVL to
individual ports is described in the IEEE 802.1Q standard.
Important
Considerations
■
In general, select your VLAN mode before you define your VLANs
(VLANs with an origin of static).
■
As part of the configuration procedures for a router port IP interface,
you must place the system in allClosed mode. Once you define a
router port IP interface (and the system creates the router port VLAN),
you cannot change the VLAN mode until you delete the router port IP
interface.
■
Select the VLAN mode as follows:
■
allOpen — Use this less restrictive mode if you have no security
issues about the forwarding of data between VLANs. The allOpen
mode is the default VLAN mode for all VLANs that you create. It
permits data with a unicast MAC address to be forwarded
between VLANs. For example, data received on IP VLAN 2 with a
destination of IP VLAN 3 is forwarded there.
The allOpen mode implies that the system uses a single bridge
address table for all of the VLANs on the system (the default
configuration).
■
allClosed
— Use this more restrictive mode if you are concerned
about security between VLANs. Data cannot be forwarded
between VLANs (although data can still be routed between
VLANs). The allClosed mode implies that each VLAN that you
create has its own address table. Router port IP interfaces require
allClosed mode.