Allied Telesis AT-S63 - Manual (Page 675)

AT-S63 Management Software Menus Interface User’s Guide
Section VI: Virtual LANs 675
Table 28 illustrates a simple example of the mapping of addresses to
egress ports for a MAC address-based VLAN of 6 nodes. The example
consists of four workstations, a printer, and a server. For instance,
Workstation 1 is connected to port 1 on the switch and is mapped to
egress ports 5 for the server and 6 for the printer.
Obviously, mapping source MAC addresses to egress ports can become
cumbersome if you are dealing with a MAC address-based VLAN that
encompasses a large number of ports and nodes. Fortunately, the egress
ports of a VLAN are considered as a community and, as such, need only
be designated as an egress port of one address in the VLAN to be
considered an egress port of all the addresses.
For instance, referring to the previous example, if workstation 1 sends a
packet containing an unknown destination MAC address, the switch does
not flood the packet to just ports 5 and 6, even though those are the
designated egress ports for packets from workstation 1. Rather, it floods it
out all egress ports assigned to all MAC address of the VLAN, except, of
course, for the port where the packet was received. In the example the
switch would flood the packet out ports 2 through 6.
The community characteristic of egress ports relieves you from having to
map each address to its corresponding egress port. You only need to be
sure that all egress ports in a MAC address-based VLAN are represented
at least once by being assigned to at least one address.
It is almost important to note that a MAC address must be assigned at
least one egress port to be considered a member of a MAC address-
based VLAN. VLAN membership of packets from a source MAC address
not assigned any egress ports is determined by the PVID of the port where
the packets are received.
Because egress ports are considered as a community within a VLAN, you
can simplify the mappings by assigning all of the egress ports to just one
MAC address and, for the rest of the addresses, assign just one port. This
can simplify the management tasks when adding and deleting MAC
Table 28. Mappings of MAC Addresses to Egress Ports Example
MAC address End Node
Switch Egress
Port
00:30:84:54:1A:45 Workstation 1 (Port 1) 5, 6
00:30:84:C3:5A:11 Workstation 2 (Port 2) 5, 6
00:30:84:22:67:17 Workstation 3 (Port 3) 5, 6
00:30:84:78:75:1C Workstation 4 (Port 4) 5, 6
00:30:79:7A:11:10 Server (Port 5) 1-4
00:30:42:53:10:3A Printer (Port 6) 1-4