Hi,
I'm working through my ICND 1 book (Wendell Odom CCENT/CCNA ICND 1 Official Exam Certification Guide, Second Edition). On page 484, its discussing identifying which route will be used when multiple routes are available.
Below is a snip of the output in the example:
172.16.0.0/16 is variably subnetted, 5 subnets, 4 masks
R 172.16.1.1/32 [120/1] via 172.16.25.2, 00:00:04, Serial0/1/1
R 172.16.1.0/24 [120/2] via 172.16.25.129, 00:00:09, Serial0/1/0
R 172.16.0.0/22 [120/1] via 172.16.25.2, 00:00:04, Serial0/1/1
R 172.16.0.0/16 [120/2] via 172.16.25.129, 00:00:09, Serial0/1/0
R 0.0.0.0/0 [120/3] via 172.16.25.129, 00:00:09, Serial0/1/0
The book states “In cases where a particular destination IP address falls within the IP address range for multiple routes, then you pick the route with the longest prefix length. In this case:
Destination address 172.16.4.3 matches the last two routes listed in R1's routing table in the example, with the route for 172.16.0.0/16 having the longest prefix length.â€
I wasn't clear on the term prefix length, but confirmed it just means mask, anyhow doesn't the route 172.16.0.0/22 have a longer prefix length than 172.16.0.0/16? Also, for what its worth, it the route for 172.16.0.0/22 has a better metric.
Any insight would be much appreciated, thank you!
Respectfully
Jason
