301 200 phone area

301 200 phone area.Before the VPN's end device can forward incoming plain unencrypted packets, there are a few more functions to perform. One of these functions is to encrypt the packet and then encapsulate the packet into a new IP header. This IP header uses an address that allows the router to forward this VPNIP packet across an insecure network between two VPN tunnel endpoints. where the source IP packet (including the source IP header) is also encrypted into a frame that cannot be read by illegal users.The second part of this chapter uses a slightly different approach to VPN tunnel formulation than usual, which is specific to only the tunnel portion and not to the encryption feature. The section focuses on the concept and configuration of how the router creates the tunnel and the method of encapsulating the source IP packet in another IP packet. The purpose of the method is to give a general overview of the role of tunnels, while leaving the specific security configuration to other certifications, such as CCNA security.The Concept of GRE TunnelsThis chapter focuses on a common type of IP tunnel: the Generic Routing Encapsulation (GRE), as defined in RFC2784, which defines additional headers and a new IP header that encapsulates the source packet. A GREIP tunnel is created when two connected routers located in the network work together (matching configuration parameters). The packets are then encrypted using the IPsec configuration.The concept of a GRE tunnel needs to be discussed in several ways. The first part shows how packets are routed through a GRE tunnel. the first part shows how packets are routed through a GRE tunnel. like a serial link used within a secure enterprise network. Then the workings of GRE are described.Routing the GRE TunnelThe GRE tunnel sits between two routers, and the nature of how this tunnel works is very similar to the nature of how a serial link forwards packets. So before discussing the GRE tunnel, review the characteristics of the routers and serial links that were previously covered (as shown in Figure 7-5).Destination address = 10.1.2.2Figure 7-5 Routing packets over a serial linkThe small network shown in Figure 7-5 is part of most enterprise networks. The network address is a private IP address (network 10.0.0.0)