Figure 1-69 shows this operation.
Figure 1-69 Layer 2 Passes to ARP
Using the information in the ARP request, ARP updates its table. Figure 1-70 shows this
operation.
Figure 1-70 ARP Adds Sending Information to Table
Layer 2: I just got a frame with a broadcast MAC, so I??™ll process it.
The protocol ID indicates that it belongs to ARP. Let me strip the
Layer 2 header and send it to ARP.
DST MAC
Broadcast
ARP
Request
SRC MAC
0800:0222:2222
Packet
Parking Lot
Layer 3 = 192.168.3.1
Layer 2 = 0800:0222:2222
Layer 3 = 192.168.3.2
Layer 2 = 0800:0222:1111
Layer 2: ARP, here is something for you.
ARP
Request Packet
Parking Lot
Layer 3 = 192.168.3.1
Layer 2 = 0800:0222:2222
Layer 3 = 192.168.3.2
Layer 2 = 0800:0222:1111
ARP: I just got an ARP request from 192.168.3.1.
Let me add its IP and MAC to my ARP table.
Now I can respond.
ARP
Request Packet
Parking Lot
Layer 3 = 192.168.3.1
Layer 2 = 0800:0222:2222
Layer 3 = 192.168.3.2
Layer 2 = 0800:0222:1111
Exploring the Packet Delivery Process 93
ARP builds a response and passes it to Layer 2, telling Layer 2 to send the response to MAC
address 0800:0222:2222 (host 192.168.3.1). Figure 1-71 shows this operation.
Figure 1-71 ARP Builds a Response
Layer 2 encapsulates the ARP in a Layer 2 frame using the destination MAC address
provided by ARP and the local source MAC address.
Pages:
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154