Managing Mac Address Table - H3C S5600 Series Operation Manual

Operation Manual – MAC Address Table Management
H3C S5600 Series Ethernet Switches
4) At this time, the MAC address table of the switch includes two forwarding entries
shown in
the packet instead of broadcasting it to User A through GigabitEthernet 1/0/1,
because MAC-A is already in the MAC address table.
Figure 1-5 MAC address table entries of the switch (2)
5) After this interaction, the switch directly unicasts the packets destined for User A
and User B based on the corresponding MAC address table entries.
Note:
Under some special circumstances, for example, User B is unreachable or User B
receives the packet but does not respond to it, the switch cannot learn the MAC
address of User B. Hence, the switch still broadcasts the packets destined for User
B.
The switch learns only unicast addresses by using the MAC address learning
mechanism but directly drops any packet with a broadcast source MAC address.

1.1.3 Managing MAC Address Table

I. Aging of MAC address table
To fully utilize a MAC address table, which has a limited capacity, the switch uses an
aging mechanism for updating the table. That is, the switch starts an aging timer for an
entry when dynamically creating the entry. The switch removes the MAC address entry
if no more packets with the MAC address recorded in the entry are received within the
aging time.
Note:
The MAC address aging timer only takes effect on dynamic MAC address entries.
With the destination MAC address triggered update function enabled, when a switch
finds a packet with a destination address matching one MAC address entry within
the aging time, it updates the entry and restarts the aging timer.
Figure 1-5. When forwarding the response packet, the switch unicasts
1-4
Chapter 1
MAC Address Table
Management