Answers: RIPv2 Basics 1

For this lab, your job is to take a working IPv4 network that has no routing protocol yet and add the RIPv2 configuration. As usual, check out the lab requirements here and take your shot at the configuration. Then check your answers here vs. my suggested answer.

Answers

Figure 1: Router Triangle Topology

Example 1: R1 Config

Example 2: R2 Config

Example 3: R3 Config

Commentary

Two fundamental duties of any network engineer will involve the configuration of IP addresses on routers and the configuration of a routing protocol. RIP is one of the simplest routing protocols to understand which is why it is often taught to new network engineers.

For this lab you were tasked with configuring RIP to ensure that each of the routers had reachability to all of these subnets in a simple design.

The requirements can be broken down into two broad categories: the commands used to enable RIP on router interfaces (using the network command), and any other commands related to RIP.

Covering the related commands first, one requirement stated that the routers should use RIP Version 2 and RIP Version 2 only. To do that, simply configure each RIP process with the version 2 command while inside router configuration mode.

The requirements also asked that you prevent routers from automatically summarizing routes at classful boundaries – a possibly a tricky phrase to unpack. In short, RIP, even RIPv2, will advertise a route for an entire classful network in cases where the router connects to multiple classful networks. All three routers use subnets of class C network 192.0.1.0 on the WAN links. Two of the routers then connect to a subnets of a different network on their LAN links (R1 and R2). As a result, R1 and R2 connect to subnets of multiple classful networks, and RIP would automatically advertise summary routes for these networks.

To avoid those summary routes, just add the no auto-summary command in RIP configuration mode on only two of the three routers (R1 and R2). R3’s three interfaces all connect to subnets of the same class C network (190.0.1.0), so the auto-summary or no auto-summary command has no impact at all on router R3.

If you try this lab on your own gear or in VIRL, watch for routes for class A networks 10.0.0.0 and 20.0.0.0 with mask /8. These routes would occur if RIP on some router had automatic summarization enabled. (Per the requirements, you should have disabled automatic summarization.)

Finally, to enable RIP on the correct router interfaces, use the network network command. IOS compares the network parameter to the interface IP addresses configured on a router. With RIP (regardless of version) the network that is configured matches a whole classful network and cannot be limited by a subnet mask or wildcard mask (as with other routing protocols). All three routers connect directly to subnets of class C network 192.0.1.0. Routers R1 and R2 connect to a subnet of another network: network 10.0.0.0 off router R1, and 20.0.0.0 off router R2. As a result, the following network commands are required:

• On R1 the two commands required would be: network 192.0.1.0 and network 10.0.0.0.
• On R2 the two commands required would be: network 192.0.1.0 and network 20.0.0.0.
• On R3 the one command required would be network 192.0.1.0.

Note that if you used extra network commands compared to those in the above list, RIPv2 would work. However, you should work to understand why other network commands on each router would not be needed. For instance, only R1 needs a network 10.0.0.0 command, because only R1 connects to a subnet of class A network 10.0.0.0.