Exploring ARP headers and fields

While in a trace file, if you enter arp in the display filter, you will most likely see a series of ARP requests and replies. Within each ARP header, there are several field values, such as Operation Code (Opcode), sender, and target IP address, which help ensure that the ARP requests/replies are received. Let's first take a look at a typical ARP transaction.

Identifying a standard ARP request/reply 

Open ARPTrace.pcapng, and take a look at the first two packets, which are the ARP request/reply. Expand each ARP request/reply, and you will see that ARP is wrapped in an Ethernet frame. However, there are no network or transport layer headers.

First, let's investigate the components of an ARP request.

Inspecting an ARP request

To view a standard ARP request, expand Frame 1. Once expanded, you can see that there are several field values, which provide information about...