1.Basic Introduction
IPSec (Internet Protocol Security) protocol is a common security protocol on the Internet. It is the most widely used security protocol standard in the development of VPN technologies in various network security solutions. It has a wide range of Mechanism and strong security.
 
2.Application

An underlying issue between IPSec tunnels and dynamic routing protocols is that dynamic routing relies on multicast or broadcast packets for routing reachability notification, whereas IPSec tunnels do not support multicast or broadcast packet encryption. Our company put forward the solution to this problem by adopting the combination of GRE and IPSec to make the configuration easier.

GRE configuration of the device:

Device 2

Parameter	Description
VPN Enable	Enable VPN Enable, select GRE
GRE tunnel name	Fill in the tunnel name
Remote IP	Fill in Remote IP
Local IP	Fill in Local IP
Local tunnel IP	Fill in the IP of the local tunnel
Remote tunnel IP	Fill in the IP of the opposite tunnel
Remote destination	Fill in the destination segment

Parameter	Description
IPSec Connection	Select the IPSec connection name or create a new IPSec
Connection name	Fill in the IPSec connection name
IPSec enable	Enable IPSec
Interface	Select the type of connection for IPSec
IPSec Networking Type	Choose IPSec networking mode, there are two options, one is the way to the site, the other is from the remote access
Authentication Type	The type of authentication here can only be pre-shared key option
PSK	Fill in a password, the remote password and the local password must be the same
Local ID Type	Choose one of the three types Default / FQDN / ID as the local ID
Local WAN IP Address/FQDN	Fill in the address of the local device WAN
Remote ID Type	Choose one of the three types Default / FQDN / ID as the remote ID
Remote WAN IP Address/FQDN	Enter the IP address of the remote device that establishes the tunnel with the local device
Local LAN IP Address/Subnet Mask Length	Enter the length of the subnet mask of the local area network
Remote LAN IP Address/Subnet Mask Length	Fill in the length of the subnet mask of the peer LAN
Policy Protocol	Choose a policy agreement, any or L2TP
Encapsulated Mode	IPSec has two encapsulation modes, one is tunnel mode and the other is transmission mode. The purpose of transmission mode is to protect end-to-end secure communication. The purpose of tunnel mode is to protect certain or all data between stations. Users can According to their actual needs of choice model.
NAT Enable	Select to enable or disable NAT disability
The First Phase
Mode	The first phase of the model there are two, one is the main mode, one is the savage mode (also known as the positive mode)
Encryption Algorithm	Choose the encryption algorithm you need
Integrity Algorithm	There are two authentication algorithms, one is SHA-1 and the other is MD5
Diffie-Hellman (DH) Group	Choose one of three key patterns from the algorithm
SA Lifetime of Phase 1	The life cycle of SA is 10800 by default, you can set it yourself
DPD	Select to enable or disable DPD, the default DPD is disabled
The Second Phase
Encryption Algorithm	Choose the encryption algorithm you need
Integrity Algorithm	There are two authentication algorithms and the first phase, one is SHA-1, the other is MD5
SA Lifetime of Phase 2	The life cycle of SA is 10800 by default, you can set it yourself
PFS	Select to enable or disable PFS, the default DPD is Enabled.