168.3.2
Layer 2 = 0800:0222:1111
Layer 3 = 192.168.3.1
Layer 2 = 0800:0222:2222
Exploring the Packet Delivery Process 149
The switch learns the port mapping for the source host by reading the source MAC address
in the ARP broadcast reply frame. So the switch adds this new source MAC address and the
port that it learned it on to the port-mapping table or MAC address table.
In this case: 0800:0222:1111 = port 2.
Because the new destination MAC address being replied to was previously added to the
switch??™s MAC table, the switch can now forward the reply frame back out port 1, and only
out port 1, because it knows what port the desired MAC address ???lives??? on, or is connected
to. This is shown in Figure 2-11.
Figure 2-11 Host Receives ARP Response
After the sender receives the ARP response, it populates its own ARP cache and then moves
the packet out of the parking lot and places the appropriate Layer 2 destination MAC
address on the frame for delivery, as shown in Figure 2-12.
As the data is sent to the switch, the switch recognizes that the destination MAC address of
the receiver is connected out a particular port, and it sends only the frame out that port to
the receiver, where it is received and deencapsulated.
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