Switching and Bridging Argumentation 19
Switching and Bridging Logic
In this affiliate so far, you accept been reminded about the cabling capacity for Ethernet forth with
the formats and meanings of the fields central Ethernet frames. A switch’s ultimate ambition is to deliver
those frames to the adapted destination(s) based on the destination MAC abode in the frame
header. Table 1-7 summarizes the argumentation acclimated by switches back forwarding frames, which differs
based on the blazon of destination Ethernet abode and on whether the destination abode has been
added to its MAC abode table.
Table 1-7 LAN About-face Forwarding Behavior
For unicast forwarding to assignment best efficiently, switches charge to apperceive about all the unicast MAC
addresses and out which interface the about-face should advanced frames beatific to anniversary MAC address.
Switches apprentice MAC addresses, and the anchorage to accessory with them, by account the antecedent MAC
address of accustomed frames. You can see the acquirements action in Example 1-2, forth with several
other capacity of about-face operation. Figure 1-6 lists the accessories in the arrangement associated with
Example 1-2, forth with their MAC addresses.
Figure 1-6 Sample Arrangement with MAC Addresses Shown
Type of
Address About-face Action
Known unicast Forwards anatomy out the distinct interface associated with the destination address
Unknown unicast Floods anatomy out all interfaces, except the interface on which the anatomy was
received
Broadcast Floods anatomy analogously to alien unicasts
Multicast Floods anatomy analogously to alien unicasts, unless multicast optimizations are
configured
PC1
SW1
VLAN 1:
IP Abode 10.1.1.1
MAC Abode 000a.b7dc.b78d
VLAN 1:
IP Abode 10.1.1.4
R4 MAC Abode 000f.2343.87c0
0/13
000a.b7dc.b78d
0200.3333.3333
0200.4444.4444
000f.2343.87cd
0/13
R3
0/6
0/4
0/3
0010.a49b.6111
SW4