From our previous example CCNA Tutorial on how to configure for static routing, we’ve learned that configuration is quite easy. However, in numerous amount of routers, this method is not practical and quite difficult to manage. Therefore, we will try to use and configure on how to do a dynamic routing.
The main purpose of routing is for path determination and packet switching. In other words, routing makes routers share its information about routes to other networks, which will be used for choosing the best path by which to transmit data from one point going to another.
In order to build a route for routing, its primary requirement is the routing protocol that will be configured on Cisco routers. One of the most common routing protocol used for dynamic routing is the RIP. The Routing Information Protocol commonly known as RIP use hop count as a method for advertising (publishing) networks. A hop count measures how many routers a packet must pass through to travel from Point A going to Point B.
As we have mentioned earlier, RIP advertised network addresses to other neighboring routers. Thus, it is a must that you know which among the available network addresses are needed to be advertised to neighboring routers for security reason.
Now, lets have a look at the figure
This network diagram was used in our previous example, static routing configuration. We will use this again so that we can compare which is better, static routing or dynamic routing.
Without RIP, routers would only know network information of those directly connected to it and none of the remote networks. Therefore, R1 knows network addresses 126.96.36.199 as well as 192.168.0.0 but not 10.0.0.0. The same goes to R2, it knows network addresses 188.8.131.52 and 10.0.0.0 but not 192.168.0.0. For routers to advertise its own network is to use RIP on each of the routers.
There are two versions of RIP in Cisco routers. RIPv1 does not share subnet mask information with its neighbors and RIPv2 publishes subnet mask information. Therefore, RIPv1 does not support subnetted networks and will only advertise classful network addresses.
1. Enable RIP. In the user EXEC mode, use the command enable to switch into privileged EXEC mode and config term to go to the global configuration mode. Router RIP command must be entered to enable the RIP protocol. Take note that the prompt changes to (config-router)# means you’re working in routing configuration mode. Since we are working with classful networks, we don’t need to execute the command version since version 1 is the default version.
2. Advertise Your Networks. It is up to you what networks are you going to publish. Do this by using the command network <network address>. In this example we will advertise all networks attached to R1, thus, networks 192.168.0.0 and 184.108.40.206.
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R1(config)#router rip R1(config-router)#network 192.168.0.0 R1(config-router)#network 220.127.116.11 R1(config-router)#end
R2(config)#router rip R2(config-router)#network 10.0.0.0 R2(config-router)#network 18.104.22.168 R2(config-router)#end