GRE - General Routing Package
---- GRE defines in RFC1701 / RFC 1702, which specifies how to use a network layer protocol to encapsulate another network layer protocol. G
The RE tunnel is defined by the source IP address and destination IP address of both ends, which allows users to use IP package IP, IPX, AppleTalk, and support
All routing protocols such as RIP, OSPF, IGRP, EIGRP. With GRE, users can use public IP networks to connect IPX networks, AppleTa
The LK network, you can also use the retention address to interconnect, or hide the IP address of the bus network.
---- GRE contains protocol type in the header, which is used to indicate the type of passenger protocol; check and include GRE's Baotou and complete passengers.
Protocol and data; key is used to receive data to verify the received data; the serial number is used to receive the sorting and error control of the receiving end packet;
The route of this packet.
---- GRE only provides packet packages, which does not have encryption to prevent network listening and attack. So in the actual environment it often and IP
The sec is used together, providing user data encryption by IPSec, providing users with better security.
