H3C Technologies H3C SecPath F1000-E - Manual (Page 186)

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MAC Address Table Configuration
NOTE:
• Currently, MAC address table configurations relevant to interfaces only apply to Layer 2 Ethernet
interfaces.
• This manual covers only the management of static, dynamic and blackhole unicast MAC address table
entries. The management of multicast MAC address entries is not introduced here.
Overview
A device maintains a MAC address table for frame forwarding. Each entry in this table indicates the
MAC address of a connected device, to which interface this device is connected and to which VLAN the
interface belongs. When forwarding a frame, the device first looks up the MAC address table by the
destination MAC address of the frame for the outgoing port. If the outgoing port is found, the frame is
forwarded rather than broadcast. Thus, broadcasts are reduced.
How a MAC Address Table Entry Is Created
A MAC address table entry can be dynamically learned or manually configured.
Dynamically learning MAC address entries
Usually, a device can populate its MAC address table automatically by learning the source MAC
addresses of received frames.
The following is how a device learns a MAC address when it receives a frame from a port, Port A for
example:
1. Check the source MAC address (MAC-SOURCE for example) of the frame. Assume that frames
with the source MAC address MAC-SOURCE can be forwarded through Port A.
2. Look up the MAC address table by the MAC address for a match and do the following:
• If an entry is found for the MAC address, update the entry.
• If no entry is found, add an entry for the MAC address to indicate from which port the frame is
received.
When receiving a frame destined for MAC-SOURCE, the device looks up the MAC address table and
forwards it from Port A.
To adapt to network changes, MAC address table entries need to be constantly updated. Each
dynamically learned MAC address table entry has a life time, that is, an aging timer. If an entry has not
updated when the aging timer expires, it is deleted. If it updates before the aging timer expires, the
aging timer restarts.