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The topology of the figure above: 4 PCs connected to switch, where PC1 and PC2 belongs to a same physical
segment (same collision domain), the physical segment connects to port 1/5 of switch; PC3 and PC4 belongs
to the same physical segment that connects to port 1/12 of switch.
The initial MAC table contains no address mapping entries. Take the communication of PC1 and PC3 as an
example, the MA C 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 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 MA C
table contains only a mapping entry of MAC address 00-01-11-11-11-11 and port1/5, and no port
mapping for 00-01-33-33-33-33 pres ent, the switch broadcast this message to all the ports in the
XGS 3-42000R(assuming all ports belong to the default VLA N1).
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 P C3, a mapping entry for MAC address 00-01-33-33-33-33 and port
1/12 is added to the MA C 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 -port1/12.
5.
After the communication bet ween P C1 and P C3, the switch does not receive any message sent
from PC1 and P C3. And t he MA C address mapping entries in the MAC table are delet ed after 300
seconds. The 300 seconds here is the default aging time for MAC address entry in switch. Aging
time can be modified in switch.
15.1.2 Forward or Filter
The Chassis Switch will forward or filter received data frames according to the MA C table. Take the above
figure as an example, assuming Chassis Switch have learnt the MAC address of P C1 and PC3, and the user
manually configured the mapping relationship for PC2 and PC4 to ports. The MAC table of Chassis 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
If PC1 sends a message to PC3, the Chassis Switch will forward the data received on port 1/5 from
port1/ 12.
2.
Filter data according to the MAC table
If P C1 sends a message to PC2, the Chassis Switch, on checking the MAC table, will find P C2 and P C1
are in the same physical segment and filter the message (i.e. drop this message).
Port number
1/5
1/5
1/12
1/12
15-2
Entry added by
Dynamic learning
Static configuration
Dynamic learning
Static configuration
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Troubleshooting
