I remember one of the things that really got me frustrated when I just started learning Cisco networking was deciphering the command output. And determining what's happening in the network based on the output of multiple command outputs that each give only a part of the story but together give you a good understanding of the condition of the network.
It can be frustrating to learn but it is a vital skill. As soon as a problem arises on a network (and it inevitably does) you will need to troubleshoot by analysing command output.
One such command is the show ip route command.
The show ip route command lists the current routing table with all the best routes to reach various subnets within an internetwork. It tells the network which can be reached through the router, what interface the data destined for that route will be sent out, the next hop router, the metric or cost to reach that network, and the administrative distance of the route discovery method.
Here's an example:
The top of the example shows a legend which identifies the meaning of various abbreviations. For instance "O" stands for OSPF, which is a popular dynamic routing protocol.
The first line reads:
This means that the route to 10.0.0.0/8 was learned (dynamically) by OSPF. You can get to that route through the neighbouring router whose IP address is 200.1.1.2 and the data will be sent out this router's Serial0/1/0 interface. The last routing update was received 16 seconds ago. The metric to reach that network is 782 and the administrative distance is 110.
OSPF has a default administrative distance of 110 as such it will be viewed as a more believable route that any other routing protocol with a higher administrative distance. But less believable than another routing protocol with a lower AD.
The metric will be compared with other metrics over other routes to determine the most efficient route so as to improve performance as much as possible.
And that's basically what you need to know about the show ip route command for the CCNA exam.
Wishing you all the best,
Roger.
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