HP VPN Concepts Guide Overview
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Hewlett-Packard Company Virtual Private Networking Concepts Guide
Note:
Note:
Note:
Note: If you divide your class C into more and more subnets, the
number of available addresses becomes smaller and smaller.
Routing Table
Routing Table
Routing Table
Routing Table
When a device creates a packet for transmission, it looks at the
destination IP address. If the address is on the same subnet as
the device (as defined by the subnet mask), the device looks for
the address on its LAN. If the destination device responds, the
originating device transmits the packet directly to the
destination. However, if the destination device is not found
locally, the originating device must decide what to do with the
packet.
The rules upon which the device bases the decision are called
routes, which are stored in a routing table. The routing table
maps network addresses to gateways. Basically, it tells the
device that if it has a packet destined for a certain network, the
packet should be sent to a specific gateway. The gateway can be
any device such as a router or a switch that can send the packet
out of the local subnet.
Static routes are entries in the routing table that do not change.
They are often defined on routers and switches when network
topologies become complex and the network administrator
wants to force packets to go in a certain known direction (that
is, through a specific gateway). Dynamic routes are entries in the
routing table that may change over time. This type of route is
usually added automatically, based on some network routing
protocol.
Default Gateway
Default Gateway
Default Gateway
Default Gateway
The routing table usually has a route of last resort known as a
default gateway. The default gateway is where the originating
device sends any packet for which it has no specific rule in its
routing table. Most desktop computers do not have static routes
added to them and therefore rely on the default gateway being
set to be able to communicate outside their local subnet. This
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