Is this RIPv1 Classless routing?

Answered Question
Mar 26th, 2007

Hello

On Monday I am retaking the CCNA exam. The first time was close to take it (I scored 809).

I have a routing question though.

In the simulator I have created the following network.

PC1-R1-R2-R3-R4-PC2.

I have subnetted 192.168.50.0 network and I have issued point-to-point addresses to each interface with mask /30.

For example R4 has IP 192.168.50.253/30 and PC2 192.168.50.254/30

Then I configured on each router, RIP with the subnetted networks.

And guess what...after 30" PC1 CAN ping PC2. How is this possible?

I thought that since RIPv1 is a classful protocol, it would require an unsubnetted network.

On the other hand, If I replace PC1 with a switch and 10 hosts, in a /28 subnet, would RIP still route routing tables?

I am confused with this detail.

On the exam, I should just enter EIGRP and it will work.

But what do you think?

Can anybody help me?

Correct Answer by sundar.palaniappan about 9 years 11 months ago

You are correct in that RIP v1 doesn't subnet mask info in routing updates. However, it does support fixed length subnet mask. You have done exactly that in your scenario.

In your scenario, you have configured all the subnets with a /30 bit mask for a major network address and thus the router would advertise them as 192.168.50.248, 192.168.50.252 and so on. The router that gets the update would know what the subnet mask of the route is based on the subnet mask of the interface through which the update was received and that's all the same /30 bits.

To answer your question, using a /28 bit subnet address wouldn't work and should fail.

Good luck with your exam!!

HTH

Sundar

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Loading.
Correct Answer
sundar.palaniappan Mon, 03/26/2007 - 14:33

You are correct in that RIP v1 doesn't subnet mask info in routing updates. However, it does support fixed length subnet mask. You have done exactly that in your scenario.

In your scenario, you have configured all the subnets with a /30 bit mask for a major network address and thus the router would advertise them as 192.168.50.248, 192.168.50.252 and so on. The router that gets the update would know what the subnet mask of the route is based on the subnet mask of the interface through which the update was received and that's all the same /30 bits.

To answer your question, using a /28 bit subnet address wouldn't work and should fail.

Good luck with your exam!!

HTH

Sundar

Actions

This Discussion