Router Routing Tables

Explain the function of fields in the routing table of a router.

Router Packet Forwarding Decision

What happens when the router receives the frame from the host device?

IP Router Routing Table

There three types of routes in a router’s routing table:

• Directly Connected – These routes are automatically added by the router, provided the interface is active and has addressing.
• Remote – These are the routes the router does not have a direct connection and may be learned:
• • Manually – with a static route
  • Dynamically – by using a routing protocol to have the routers share their information with each other
• Default Route – this forwards all traffic to a specific direction when there is not a match in the routing table

Static Routing

Static Route Characteristics:

• Must be configured manually

• Must be adjusted manually by the administrator when there is a change in the topology

• Good for small non-redundant networks
• Often used in conjunction with a dynamic routing protocol for configuring a default route

Dynamic Routing

Dynamic Routes Automatically:

• Discover remote networks

• Maintain up-to-date information

• Choose the best path to the destination
• Find new best paths when there is a topology change

Dynamic routing can also share static default routes with the other routers.

Introduction to an IPv4 Routing Table

The show ip route command shows the following route sources:

• L – Directly connected local interface IP address
• C – Directly connected network
• S – Static route was manually configured by an administrator
• O – OSPF
• D – EIGRP

This command shows types of routes:

• Directly Connected – C and L
• Remote Routes – O, D, etc.
• Default Routes – S*

Other related topics

Other useful information

• Full CCNA Course
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• 200-301 CCNA Exam Questions and Solutions
• 200-301 CCNA Exam Topics