Explanation
A digital certificate refers to a digital authentication that marks the identity information of the communication parties in the Internet communication, and people can use it to identify the identity of the other party on the Internet.
The CA center adopts the digital certificate authentication technology with digital encryption technology as the core. Through the digital certificate, the CA center can perform various processing such as encryption, decryption, digital signature and signature authentication for various information transmitted on the Internet.

Explanation Explanation
Neighbor Discovery Protocol (English:Neighbor Discovery Protocol for short: NDP or ND) is a part of the TCP/IP protocol stack and is mainly used together with IPv6.
The principle of NDP address resolution:
In the process of NDP address resolution, two types of ICMP packets are used: Type135: NS Neighbor Solicitation Type136: NA neighbor advertisement message In simple terms, the end that initiates active communication (A in this environmentR1) Before sending ICMP data, first send NS message, NS messageThe function of the message is to request the MAC address of the target communication address. When the peer AR2 receives the address resolution, it will actively reply to the NA message. The NA message carries AR2's own MAC address to complete the resolution.
NS message parsing:
The source address is the interface address of AR1, and the destination address is the requesting node multicast group of the AR2 address. Type: 135 Target Address: 2012::2, the destination address of the required request. Source link-layer addres: Source link layer address, MAC address.
So thisThe meaning of the NS message is that the source 2012::1 needs to resolve the MAC address of the destination address 2012::2. My own MAC address is 00:E0:FC:FB:66:05. Please reply to me when you receive it.
NA packet parsing:
The source address is the interface address of AR2, and the destination address is the interface address of AR1.
At this time, AR2 has learned the IP address and MAC address of the source AR1 through NS packets, so it can be sent by unicast.
Type: NA message, 136
Target Address: The requested address.
Target link-layer address: The MAC address of the requested address.
So thisThe NA message means that 2012::1 needs to request the link layer address of the target address
2012::2 is 00:E0:FC:7D:5F:96. This completes bidirectional address resolution.