Route summarization

bornwith

I am trying to summarize two networks and create a static route.

The networks are

172.16.3.0 /24 and 172.16.4.0/24

i summarized them as 172.16.3.0/23.

But it when I try to create the static route I get an error.

iP route 172.16.3.0 255.255.254.0 201.10.4.9

i get an Inconsistent address and mask error.

I can create individual routes for each of the /24 network without a problem.

I am using PT 7.2

TIA

OfWolfAndMan

That's because your subnetting is off. Remember that each byte starts at 0, not 1. Therefore, using a 255.255.254.0 mask, your subnet ranges would look like this:
-172.16.0.0/23
-172.16.2.0/23

Its best to use two /24s in this situation. You could use a /21, but not recommended in real life. Here's what the configs should look like:
-Option 1: create two separate routes:
ip route 172.16.3.0 255.255.255.0 201.10.4.9
ip route 172.16.4.0 255.255.255.0 201.10.4.9
-Option 2: create aggregate address and catch unavailable prefixes at next hop with bit bucket:
ip route 172.16.0.0 255.255.248.0 201.10.4.9
(At the next hop router, 201.10.4.9)
ip route 172.16.0.0 255.255.248.0 null0

hope that helped.

bornwith

OfWolfAndMan wrote: »

That's because your subnetting is off. Remember that each byte starts at 0, not 1. Therefore, using a 255.255.254.0 mask, your subnet ranges would look like this:
-172.16.0.0/23
-172.16.2.0/23

Its best to use two /24s in this situation. You could use a /21, but not recommended in real life. Here's what the configs should look like:
-Option 1: create two separate routes:
ip route 172.16.3.0 255.255.255.0 201.10.4.9
ip route 172.16.4.0 255.255.255.0 201.10.4.9
-Option 2: create aggregate address and catch unavailable prefixes at next hop with bit bucket:
ip route 172.16.0.0 255.255.248.0 201.10.4.9
(At the next hop router, 201.10.4.9)
ip route 172.16.0.0 255.255.248.0 null0

hope that helped.

thank you for your time

yeah it showed me I had a flawed understanding of how subnetting works ��