HP VPN Firewall Appliances VPN Configuration Guide

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Figure 5 Network diagram
Constructing VPN
As shown in Figure 6, Site 1 and Site 2 both belong to VPN 1 and are located in different cities. Using
a GRE tunnel can connect the two VPN sites across the WAN.
Figure 6 Network diagram
Operating with IPsec
As shown in Figure 7, GRE can be encapsulated into IPsec to improve transmission security for routing
protocol packets, voice data, and video data.
Figure 7 Network diagram
For more information about IPsec, see Security Configuration Guide.
Protocols and standards
• RFC 1701, Generic Routing Encapsulation (GRE)
• RFC 1702, Generic Routing Encapsulation over IPv4 networks
Device A
Device B Device C
Device D
Host A Host B
IP network
GRE tunnel
IP network
IP network