Arp Table - HP 10500 Series Configuration Manual

Host A looks through its ARP table for an ARP entry for Host B. If an entry is found, Host A uses the
1.
MAC address in the entry to encapsulate the IP packet into a data link layer frame and sends the
frame to Host B.
If Host A finds no entry for Host B, Host A buffers the packet and broadcasts an ARP request. The
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payload of the ARP request comprises the following information:
Sender IP address and sender MAC address—Host A's IP address and MAC address
Target IP address—Host B's IP address
Target MAC address—An all-zero MAC address
All hosts on this subnet can receive the broadcast request, but only the requested host (Host B)
processes the request.
Host B compares its own IP address with the target IP address in the ARP request. If they are the
3.
same, Host B performs the following:
Adds the sender IP address and sender MAC address into its ARP table.
a.
Encapsulates its MAC address into an ARP reply.
b.
Unicasts the ARP reply to Host A.
c.
After receiving the ARP reply, Host A performs the following:
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Adds the MAC address of Host B into its ARP table.
a.
Encapsulates the MAC address into the packet and sends the packet to Host B.
b.
Figure 2 ARP address resolution process
If Host A and Host B are on different subnets, the resolution process is as follows:
Host A sends an ARP request to the gateway. The target IP address in the ARP request is the IP
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address of the gateway.
The gateway responds with its MAC address in an ARP reply to Host A.
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Host A uses the gateway MAC address to encapsulate the packet and sends the packet to the
3.
gateway.
If the gateway has the ARP entry for Host B, it forwards the packet to Host B directly. If not, it
4.
broadcasts an ARP request, in which the target IP address is the IP address of Host B.
After obtaining the MAC address of Host B, the gateway sends the packet to Host B.
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ARP table

An ARP table stores dynamic and static ARP entries.
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