The following figure shows what the ARP protocol is.

In ARP, there is a kind of scheme called Wuwei ARP. So what is the role of such ARP protocols? Next we will introduce it in detail. We hope that our introduction will help you understand this concept. Gratuitous ARP for no reason, GARP) ARP is also known as the Wuwei ARP protocol. The host sometimes uses its own IP address as the target address to send ARP requests. This ARP request is called the Wuwei ARP Protocol. GARP has two main purposes:

1) Check the duplicate address. If an ARP response is received, the duplicate address exists ).

2) It is used to advertise a new data link identifier. When a device receives an arp request and finds that there is an IP address of the sender in the arp buffer, It updates the MAC address entry of this IP address.

Displays the MAC address and IP address package of a Cisco router that declares its Ethernet interface Ethernet 0 to the network during the boot process after it is powered on.

No ARP Protocol

It can be seen that the type encoding of this ARP packet is 2, which indicates an ARP response message but no ARP request message for this IP address is provided before ). The source hardware address MAC address of this ARP packet) is the MAC address of this interface of the router, the target hardware address MAC address) uses the broadcast address FF-FF-FF-FF-FF-FF); and the source and target Protocol address IP address) is the IP address of this interface. This ARP packet is used by the device router to declare its IP address and MAC address ing to the network, and also to check whether there are duplicate IP addresses.