Elements and Functions of a MAC Address Table
Elements
Each entry in a MAC address table is identified by a MAC address and a VLAN ID or VSI. When a destination host joins multiple VLANs or VSIs, the host's MAC address corresponds to multiple VLAN IDs or VSIs in the MAC address table. Table 2-2 lists four MAC address entries, which specify the outbound interfaces for packets with specified destination MAC addresses and VLAN IDs or VSI names. For example, the first MAC address entry is used to forward the packets with destination MAC address 0011-0022-0034 and VLAN 10 through outbound interface 10GE3/0/1.
Functions
A MAC address table is used for unicast forwarding of packets. In Figure 2-1, when packets sent from PC1 to PC3 reach the switch, the switch searches its MAC address table for the destination MAC address MAC3 and VLAN 10 in the packets to obtain outbound interface Port3. The switch then forwards packets to PC3 from Port3.
