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Static Routing

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الكلية كلية تكنولوجيا المعلومات     القسم قسم شبكات المعلومات     المرحلة 4
أستاذ المادة وسام سمير عبد علي بهيه       11/03/2013 21:48:04
Static Routing


In this lecture, you will learn to:
Define the general role a router plays in networks.
Describe the directly connected networks and the different router interfaces.
Examine directly connected networks in the routing table and use the CDP protocol.
Describe static routes with exit interfaces.
Describe summary and default route.
Examine how packets get forwarded when using static routes.
Identify how to manage and troubleshoot static routes.

Static routes are commonly used when routing from a network to a stub network. A stub network is a network accessed by a single route.

Routing Table Principles
Principle 1:
"Every router makes its decision alone, based on the information it has in its own routing table.“
R1 has three static routes in its routing table and makes forwarding decisions based solely upon the information in the routing table. R1 does not consult the routing tables in any other routers. Nor does it know whether or not those routers have routes to other networks. Making each router aware of remote networks is the responsibility of the network administrator.

Principle 2:
"The fact that one router has certain information in its routing table does not mean that other routers have the same information.“
R1 does not know what information other routers have in their routing table.
Using Principle 2, we still need to configure the proper routing on the other routers (R2 and R3) to make sure that they have routes to these three networks.

Principle 3:
"Routing information about a path from one network to another does not provide routing information about the reverse, or return path.“
Most of the communication over networks is bidirectional. This means that packets must travel in both directions between the end devices involved. A packet from PC1 may reach PC3 because all the routers involved have routes to the destination network 192.168.2.0/24. However, the success of any returning packets going from PC3 to PC1 depends upon whether or not the routers involved have a route to the return path, PC1 s 172.16.3.0/24 network.
Using Principle 3 as guidance, we will configure proper static routes on the other routers to make sure they have routes back to the 172.16.3.0/24 network.


Resolving to an Exist Interface
Recursive Route Lookup
Before any packet is forwarded by a router, the routing table process must determine the exit interface to use to forward the packet. This is known as route resolvability.

For more Information, please download PPT file


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