3Com 4007, Руководство по внедрению, Страница: 261 / 684

VLAN allOpen or allClosed Mode 261
VLAN allOpen or
allClosed Mode
The VLAN mode affects the way in which a module address table is used.
You can select allOpen or allClosed as the VLAN mode for the switch
fabric module or for any Layer 2 or Multilayer switching module. The
default is
allOpen
. VLAN modes on a module cannot be mixed; they
must be either allOpen or allClosed for a module.
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 of choosing one VLAN mode per module;
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
on a Multilayer Switching Module, you must place the system in
allClosed mode. After 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 a 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. The
allOpen mode implies that the module uses a single bridge address
table for all of the VLANs on the module (the default
configuration). If a device is a member of two VLANs, and the
VLAN mode is
allOpen
, the address table discards the device
address and learns the new address each time that the device
transmits on the other VLAN.
On Multilayer switching modules, allOpen mode permits untagged
data with a unicast MAC address to be forwarded between VLANs,
if the destination MAC address is in the forwarding table.
Example: Untagged data received on IP VLAN 2 with a destination
of IP VLAN 3 is forwarded there.