Subnet of 64.110.78.97/30 not working?

[Jonathan1337]

Hello, this is what I'm trying to solve.. it is a given topology and the two addresses (64.110.77.97/30 & 64.110.78.97/30) are required. I'm having problems setting up the ip addresses. If I have 64.110.77.97/30 that means 64.110.77.98 & 64.110.77.99 should be the two available host slots, right? But when I try to assign the .99 address to the s0/0 on the "Praha" router it tells me that 64.110.77.99/30 is bad mask.

Can anyone tell me what am I doing wrong? Or what ip address should the s0/0 at the "praha" router have and what should be assigned to s0/0 on "Internet". Thanks for all the comments.

[Jonathan1337]

I think I've just solved it bymyself since it is /30 the increment is 4 and I shouldn't start from 97, but from 0 right?

So it starts as 64.110.77.0 - 64.110.77.3 and by repeating this I end up at 64.110.77.96 - 64.110.77.99 and that means, that the address I was giving isnt a network ID but already one of the host available addresses, because the network ID is 64.110.77.96 and 64.110.77.99 is broadcast, therefore I should be using .97 & .98 for the two points. Am I right?

[darren.g]

Jonathan Statham wrote:
I think I've just solved it bymyself  since it is /30 the increment is 4 and I shouldn't start from 97, but from 0 right?
So it starts as 64.110.77.0 - 64.110.77.3 and by repeating this I end up at 64.110.77.96 - 64.110.77.99 and that means, that the address I was giving isnt a network ID but already one of the host available addresses, because the network ID is 64.110.77.96 and 64.110.77.99 is broadcast, therefore I should be using .97 & .98 for the two points. Am I right?

Yup, you sure are.

The addresses for the given subnet are as follows

64.110.77.96    <--- Subnet Address

64.110.77.97    <--- Node Address

64.110.77.98    <--- Node Address

64.110.77.99    <--- Broadcast Address

Your two "usable" IP addresses are .97 & .98 - .96 is your 'network, and .99 your broadcast address in that subnet.

Download the Solar Winds Advanced Subnet calculator (it's free) - it helps if you don't have VLSM straight in your head like us old buggers do. :-)

Cheers.