Forward Or Filter - Digitalchina Networks DCS-3950 series Manual

The topology of the figure above: 4 PCs connected to DCS-3950 series switch, where
PC1 and PC2 belongs to a same physical segment (same collision domain), the physical
segment connects to port 5 of DCS-3950 series switch; PC3 and PC4 belongs to the
same physical segment that connects to port 12 of DCS-3950 series switch.
The initial MAC table contains no address mapping entries. Take the communication
of PC1 and PC3 as an example, the MAC address learning process is as follow:
1. When PC1 sends message to PC3, the switch receives the source MAC address
00-01-11-11-11-11 from this message, the mapping entry of 00-01-11-11-11-11 and
port 5 is added to the switch MAC table.
2. At the same time, the switch learns the message is destined to 00-01-33-33-33-33, as
the MAC table contains only a mapping entry of MAC address 00-01-11-11-11-11 and
port 5, and no port mapping for 00-01-33-33-33-33 present, the switch broadcast this
message to all the ports in the switch (assuming all ports belong to the default
VLAN1).
3. PC3 and PC4 on port 12 receive the message sent by PC1, but PC4 will not reply, as
the destination MAC address is 00-01-33-33-33-33, only PC3 will reply to PC1. When
port 12 receives the message sent by PC3, a mapping entry for MAC address
00-01-33-33-33-33 and port 12 is added to the MAC table.
4. Now the MAC table has two dynamic entries, MAC address 00-01-11-11-11-11 - port
5 and 00-01-33-33-33-33 -port 12.
5. After the communication between PC1 and PC3, the switch does not receive any
message sent from PC1 and PC3. And the MAC address mapping entries in the MAC
table are deleted after 300 seconds. The 300 seconds here is the default aging time
for MAC address entry in DCS-3950 series switch. Aging time can be modified in
DCS-3950 switch.

8.1.2 Forward or Filter

The switch will forward or filter received data frames according to the MAC table.
Take the above figure as an example, assuming DCN switch have learnt the MAC address
of PC1 and PC3, and the user manually configured the mapping relationship for PC2 and
PC4 to ports. The MAC table of DCN switch will be:
MAC Address
00-01-11-11-11-11
00-01-22-22-22-22
00-01-33-33-33-33
00-01-44-44-44-44
1. Forward data according to the MAC table
DCS-3950 series Ethernet switch manual
Fig 8.1 Dynamic Learning of MAC addresses.
Port number
5
5
12
12
Entry added by
Dynamic learning
Static configuration
Dynamic learning
Static configuration
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