Enterasys Networks 802.1Q - Manual (Page 74)

Example 4, Isolating Network Traffic According to Protocol
4-14 Examples
8. Bridge 1 receives the frame and recognizes User B’s MAC address. The frame is forwarded to
the correct port and the bridge’s Source Address Table is updated with an entry for the Mail
Server’s MAC address. User B receives the Mail Server’s response. Any further unicast traffic
between the Mail Server and User B will be handled in the same fashion by the switches in the
network.
4.4 EXAMPLE 4, ISOLATING NETWORK TRAFFIC ACCORDING TO
PROTOCOL
This final example illustrates how to restrict AppleTalk protocol traffic of a network to prevent
unwanted multicast frames from slowing down the whole network and yet be able to send and
receive frames associated with other protocols.
In this example, illustrated in Figure 4-7 , the Publications Department is relocating from another
site to the third floor. This network will consist of six computers and a printer using several
protocols including the AppleTalk protocol. A characteristic of the AppleTalk protocol is to send
all frames as multicast frames. These multicast frames will be isolated to a VLAN (Grey VLAN)
to prevent them from slowing down the other networks.
A second VLAN (Yellow VLAN) will be established to handle traffic of other protocols. The
Publications Department users will have access to the mail server on the first floor along with the
Red, Blue, and Green VLANs.