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Fig 7-1 MAC Table dynamic learning
The topology of the figure above: 4 PCs connected to ES4700 series, where PC1
and PC2 belongs to a same physical segment (same collision domain), the physical
segment connects to port 1/5 of ES4700 series; PC3 and PC4 belongs to the same
physical segment that connects to port 1/12 of ES4700 series.
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 sendsa 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 1/5 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 1/5, 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 1/12 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 1/12 receives the message sent by PC3, a mapping entry for MAC
address 00-01-33-33-33-33 and port 1/12 is added to the MAC table.
4. Now the MAC table has two dynamic entries, MAC address 00-01-11-11-11-11 - port
1/5 and 00-01-33-33-33-33 -port 1/12.
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 ES4700 series. Aging time can be modified in ES4700
PC1
MAC 00-01-11-11-11-11
PC4
MAC 00-01-44-44-44-44
PC3
MAC 00-01-33-33-33-33
PC2
MAC 00-01-22-22-22-22
1/5
1/12
