connected. GRE offers no encryption, but it does forward broadcasts and multi- casts. If you want a routing protocol to establish a neighbor adjacency or exchange routes through a tunnel, you'll probably need to configure GRE. GRE tunnels are often built within VPN tunnels to take advantage of encryption. GRE is described in RFCs 1701 and 2784. VPN tunnels are also designed to allow remote networks to appear as if they were locally connected. VPN encrypts all information before sending it across the network, but it will not usually forward multicasts and broadcasts. Conse- quently, GRE tunnels are often built within VPNs to allow routing protocols to function. VPNs are often used for remote access to secure networks. There are two main types of VPNs; point-to-point and remote access. Point-to-point VPNs offer connectivity between two remote routers, creating a virtual link between them. Remote-access VPNs are single-user tunnels between a user and a router, firewall, or VPN concentrator (a specialized VPN-only device). Remote-access VPNs usually require VPN client software to be installed on a personal computer. The client communicates with the VPN device to establish a personal virtual link. SSH is a client/server application designed to allow secure connectivity to servers. In practice, it is usually used just like telnet. The advantage of SSH over telnet is that it encrypts all data before sending it. While not originally designed to be a tunnel in the sense that VPN or GRE would be considered a tunnel, SSH can be used to access remote devices in addition to the one to which you have connected. While this does not have a direct application on Cisco routers, the concept is similar to that of VPN and GRE tunnels, and thus worth mentioning. I use SSH to access my home network instead of a VPN. Tunnels can encrypt data SO that only the other side can see it, as with SSH, or they can make a remote network appear local, as with GRE, or they can do both, as is the case with VPN. GRE tunnels will be used for the examp