![]() A major difference is that GRE tunnels allow multicast packets to traverse the tunnel whereas IPSec VPN does not support multicast packets. While many might think a GRE IPSec tunnel between two routers is similar to a site to site IPSec VPN (crypto), it is not. The diagram below shows the encapsulation procedure of a simple - unprotected GRE packet as it traversers the router and enters the tunnel interface: If data protection is required, IPSec must be configured to provide data confidentiality – this is when a GRE tunnel is transformed into a secure VPN GRE tunnel. It is important to note that packets travelling inside a GRE tunnel are not encrypted as GRE does not encrypt the tunnel but encapsulates it with a GRE header. With GRE, a virtual tunnel is created between the two endpoints (Cisco routers) and packets are sent through the GRE tunnel. When the IPSec client initiates the VPN tunnel connection, the IPSec server pushes the IPSec policies to the IPSec client and creates the corresponding VPN tunnel connection.Generic Routing Encapsulation ( GRE) is a tunneling protocol developed by Cisco that allows the encapsulation of a wide variety of network layer protocols inside point-to-point links.Ī GRE tunnel is used when packets need to be sent from one network to another over the Internet or an insecure network. ![]() Network extension mode allows users at the central site (where the VPN 3000 series concentrator is located) to access network resources on the client site.Īfter the IPSec server has been configured, a VPN connection can be created with minimal configuration on an IPSec client, such as a supported Cisco 870 series access router. Resources at the client site are unavailable to the central site. Client mode is the default configuration and allows only devices at the client site to access resources at the central site. The Cisco Easy VPN client feature can be configured in one of two modes-client mode or network extension mode. Easy VPN server-enabled devices allow remote routers to act as Easy VPN Remote nodes. This protocol allows most VPN parameters, such as internal IP addresses, internal subnet masks, DHCP server addresses, WINS server addresses, and split-tunneling flags, to be defined at a VPN server, such as a Cisco VPN 3000 series concentrator that is acting as an IPSec server.Īn Easy VPN server-enabled device can terminate VPN tunnels initiated by mobile and remote workers who are running Cisco Easy VPN Remote software on PCs. The Cisco Easy VPN client feature eliminates much of the tedious configuration work by implementing the Cisco Unity Client protocol. Figure 6-1 shows a typical deployment scenario. ![]() ![]() The example in this chapter illustrates the configuration of a remote access VPN that uses the Cisco Easy VPN and an IPSec tunnel to configure and secure the connection between the remote client and the corporate network. Remote access VPNs are used by remote clients to log in to a corporate network. Site-to-site VPNs are used to connect branch offices to corporate offices, for example. Two types of VPNs are supported-site-to-site and remote access. The Cisco 870 series routers support the creation of Virtual Private Networks (VPNs).Ĭisco routers and other broadband devices provide high-performance connections to the Internet, but many applications also require the security of VPN connections which perform a high level of authentication and which encrypt the data between two particular endpoints. Configuring a VPN Using Easy VPN and an IPSec TunnelĪpply Mode Configuration to the Crypto MapĬonfigure the IPSec Crypto Method and ParametersĪpply the Crypto Map to the Physical Interface ![]()
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