3Com 4007, Implementation Manual, Page: 262 / 684

262 C
HAPTER
14: V
IRTUAL
LAN
S
(VLAN
S
)
■
allClosed — Use this 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. If a device is a member of two VLANs, and the VLAN
mode is
allClosed
, the device address is retained in both address
tables. Unnecessary relearning by the address table is prevented,
but data cannot be forwarded between VLANs. Router port IP
interfaces require allClosed mode.
■
If you are using allClosed mode and STP on a Multilayer Switching
Module (with multiple routes to a destination), you can also specify
the mode called
Ignore STP mode to disable STP blocking for a
specified static VLAN. (Although each VLAN has its own address table,
there is only one STP on the module.) See “Ignore STP Mode” later in
this chapter for information on this mode. (To disable STP blocking on
a per-port basis with allOpen or allClosed VLANs, you can use the
bridging option
bridge port stpState
on the Administration
Console). See Chapter 9 for bridging information.
■
Your selection of a VLAN mode affects how you manipulate bridge
port addresses. Examples:
■
If you select allClosed mode, you must specify a VLAN interface
index to identify the appropriate bridge address table.
■
If you select allOpen mode (the default), only one address table
exists for the entire module, so you can manipulate the bridge port
addresses without specifying a VLAN interface index.
VLANs on a module are either allOpen or allClosed. You select the VLAN
mode on the Administration Console by using the
bridge vlan mode
command. Because each mode has its own set of rules, a Switch 4007
system may contain mixed modules of different modes. The chassis may
contain VLANs on some modules that are
allOpen and VLANs on other
modules that are allClosed .