Extranet server System Considerations

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6.3.3 The Guts

Lets look at the structure for information provided by the AltaVista Tunnel.

6.3.3.1 AltaVista Tunnel Extranet server

The tunnel server consists of three integral parts that allow it to function as a router for tunnel sessions: Routing tables The routing table maps a range of local physical IP addresses to hosts on the local network that will receive tunnel traffic. A defined route may be set as a default route for all tunnel groups, or dynamically assigned as needed to one or many groups. A default route for all tunnel groups would allow those groups to access the same hosts on the enterprise LAN or WAN, whereas a dynamically assigned configuration would allow certain groups to access specific ranges of IP addresses on the network. The routing table on the tunnel server consists of three parts: • Subnet: This is the subnet of the network addresses on the local network that are part of the tunnel. Traffic destined for these IP addresses will use the tunnel network. • Netmask: This is the Netmask corresponding to the assigned subnet. • Description: A unique designation assigned to this route. Dynamic IP tables Each dynamic range of IP addresses can be routed to the physical IP addresses listed in the tunnel servers routing table. The dynamic IP addresses are virtual. The server assigns one IP address to the client requesting a tunnel session, and a second to the servers end of the tunnel session. The server end of the tunnel session is then routed to the physical IP range configured in the routing table. Each tunnel group has its own range of dynamic virtual IP addresses, and each of these ranges may be routed to the same or different physical IP addresses, as needed. Each dynamic IP address range has five definable parameters: • Range name : This name is arbitrary and assigned by the system administrator for defining the IP range in a manageable way. • Range description : A brief description of the IP range i.e., IPs for the Sales Tunnel. This is useful when managing many dynamic IP ranges on the same server. • First IP : This is the lowest IP address in the dynamic IP range, and thus the first usable IP address within the range. • Total tunnels : This value is the total number of tunnel sessions available at any given time. The total number of IP addresses that can be dynamically assigned is twice that of the Total Tunnels setting one IP address per end of the tunnel. • NetMask : The network mask that corresponds to the total group of usable IP addresses in the dynamic range.