Finding # of classfull network from Summarized IP address.

Grace-CCNA

Hello,

Can someone helps to know why the answer is 8? I do not know how to find the # classfull IPs. Thanks.

[h=4]How many classful networks are summarized by the static summary route ip route 192.168.32.0 255.255.248.0 S0/0/0?[/h]

• 2
• 4
• 8
• 16

GDaines

A 248 mask gives a block size of 32, so that would allow for 8 subnets, so the answer being 8 doesn't surprise me. As the rest of my answer was wrong I've removed it to avoid confusion as another answer has been given.

james43026

Here is how this breaks down.

Look at the network address of 192.168.32.0 and subnet mask of 255.255.248.0 that are both given. Based on that subnet mask what is the range? It would be 8, this is based on the binary of the third octet of the subnet mask being 11111000, the last bit that is a 1, is the bit that converts to a decimal value of 8, this is the number that defines our range.

192.168.32.0/24= starting address
192.168.33.0/24
192.168.34.0/24
192.168.35.0/24
192.168.36.0/24
192.168.37.0/24
192.168.38.0/24
192.168.39.0/24= last address being summarized.

These are the 8 classful networks that are being summarized by this route. Keep in mind though, that this route is NOT classful, and the question is a bit misleading, because it's not like you would actually use this with a classful routing protocol like RIPv1. You would still be using this summary route with a classless routing protocol.

d4nz1g

i hate this classful way of thinking

sschwieterman

james43026 wrote: »

Here is how this breaks down.

Look at the network address of 192.168.32.0 and subnet mask of 255.255.248.0 that are both given. Based on that subnet mask what is the range? It would be 8, this is based on the binary of the third octet of the subnet mask being 11111000, the last bit that is a 1, is the bit that converts to a decimal value of 8, this is the number that defines our range.

192.168.32.0/24= starting address
192.168.33.0/24
192.168.34.0/24
192.168.35.0/24
192.168.36.0/24
192.168.37.0/24
192.168.38.0/24
192.168.39.0/24= last address being summarized.

These are the 8 classful networks that are being summarized by this route. Keep in mind though, that this route is NOT classful, and the question is a bit misleading, because it's not like you would actually use this with a classful routing protocol like RIPv1. You would still be using this summary route with a classless routing protocol.

Grace-CCNA, james43026 has the correct answer here.