3Com 4007, Implementation Manual, Page: 274 / 684

274 C
HAPTER
14: V
IRTUAL
LAN
S
(VLAN
S
)
Example 3: VLANs with Tagged Front-Panel Ports
The configuration in Figure 17 shows multiple overlapping VLANs that
span two 20-port Layer 2 switching modules and pass traffic through the
switch fabric module (which resides in slot 7 but is logically represented
above the other modules).
In this example:
■
There are two user-defined VLANs: VLAN2 and VLAN3. For the
purposes of this example, assume that the default VLAN exists but is
tagged on all ports that are shared by one or both of the
user-configured VLANs. (You can also remove the shared ports from
the default VLAN or remove the default VLAN.)
■
VLAN2 and VLAN3 overlap on both the front-panel and backplane
ports of Module-YY and on the switch fabric module backplane port
(Port 17) that is connected to Module-YY.
■
Because the membership of both VLANs is port-based, the shared
ports (on both the front-panel and backplane ports) must be explicitly
tagged.
■
Station-E must support tagging because it is connected to a tagged
port.
■
The two overlapped front-panel ports on Module-YY can receive
frames that are flooded on VLAN2 from Station-A, Station-B, and
Station-E, or on VLAN3 from Station-C, Station-D, and Station-E.
This communication is accomplished through the switch fabric
module, which inserts an IEEE 802.1Q tag into the frame that contains
the appropriate VLAN-ID. It then forwards the frame through its
backplane port (Port 17) to Module-YY.
VLAN2:
■
VLAN Index 2
■
VID 20
■
Ports 6–10, 21/22
■
Tagging none
front-panel ports 6–10
■
Tagging
none
backplane port 21/22
VLAN2:
■
VLAN Index 2
■
VID 20
■
Ports 6–10, 21/22
■
Tagging none
front-panel ports 6–10
■
Tagging
none
backplane port 21/22
VLAN2:
■
VLAN Index 2
■
VID 20
■
Ports 1,5
■
Tagging none fabric
ports 1,5
Table 51 Port-based VLANs with Tagged Backplane Ports (continued)
Slot 1 Module Slot 2 Module Switch Fabric Module