CIDR Question...

r_durant

I had a question from a test engine...Which of the following statements are true about CIDR? and one of the true statements were...

Allows ISPs to reduce the number of routes carried in their routing table.

I would have thought CIDR would allow you to create more subnets, hence more routes in your routing table as an ISP??

iproute

r_durant wrote:

I had a question from a test engine...Which of the following statements are true about CIDR? and one of the true statements were...

Allows ISPs to reduce the number of routes carried in their routing table.

I would have thought CIDR would allow you to create more subnets, hence more routes in your routing table as an ISP??

I may be wrong but I think CIDR helps reduce the amount of routes in the routing table because of route summarization.

http://ciscotips.wordpress.com/2006/05/12/route-summarization/

mysql1988

CIDR allows you to keep routing tables smaller.

Lets say you want to assign Ip addresses to 2 seperate "60 hosts" on a network A and B

you can choose to use an address like 10.10.10.0/24 for network A and 10.10.11.0/24 for network B


or you can reduce routes in your routing table by assigning 10.10.10.0/26 for network A and
and 10.10.10.64/26 for network B

just make sure IP subnet-zero is enabled on the router

r_durant

Ok thanks, i gotcha...route summarization didn't come to mind then, i was just seeing a barrage of subnets in my mind...