SGS-6341-Series User Manual

21-107
21.1.2 Forward or Filter
The switch will forward or filter received data frames according to the MAC table. Take the
above figure for an example. Assuming switch has learned the MAC address of PC1 and PC3,
and the user manually configures the mapping relationship for PC2 and PC4 to ports. The
MAC table of switch will be:
MAC Address Port number Entry added by
00-01-11-11-11-11 1/5 Dynamic learning
00-01-22-22-22-22 1/5 Static configuration
00-01-33-33-33-33 1/12 Dynamic learning
00-01-44-44-44-44 1/12 Static configuration
1． Forward data according to the MAC table
If PC1 sends a message to PC3, the switch will forward the data received on port 1/5 from
port1/12.
2． Filter data according to the MAC table
If PC1 sends a message to PC2, the switch, on checking the MAC table, will find PC2 and PC1,
which are in the same physical segment and filter the message (i.e. drop this message).
Three types of frames can be forwarded by the switch:
 Broadcast frame
 Multicast frame
 Unicast frame
The following describes how the switch deals with all the three types of frames:
1． Broadcast frame: The switch can segregate collision domains but not broadcast
domains. If no VLAN is set, all devices connected to the switch are in the same
broadcast domain. When the switch receives a broadcast frame, it forwards the frame
in all ports. When VLANs are configured in the switch, the MAC table will be adapted
accordingly to add VLAN information. In this case, the switch will not forward the
received broadcast frames in all ports, but forward the frames in all ports in the same
VLAN.
2． Multicast frame: For the unknown multicast, the switch will broadcast it in the same
VLAN, but the switch only forwards the multicast frames to the multicast group’s port
if IGMP Snooping function or the static multicast group has been configured.
3． Unicast frame: When no VLAN is configured, if the destination MAC addresses are in
the switch MAC table, the switch will directly forward the frames to the associated
ports; when the destination MAC address in a unicast frame is not found in the MAC
table, the switch will broadcast the unicast frame. When VLANs are configured, the
switch will forward unicast frame within the same VLAN. If the destination MAC
User’s Manual of SGS-6341 series