Questions tagged as ['netmask']

I was setting up ip addresses between two devices and I noticed something odd. I feel like I am missing an important fundamental here:

Context:
Device A: 10.30.0.1/12
Device B: 10.2.0.2/12

if I set up the IP like this, then A and B cannot ping each other

However, if I do
Device A: 10.30.0.1/12
Device B: 10.30.0.2/12
OR
Device A: 10.2.0.1/12
Device B: 10.2.0.2/12

Then A and B can ping each other just fine. ...

in ipv4 cidr notation you can have an ip address like 10.10.20.0/24

it's expanded to

network  : 10.10.20.0
first ip : 10.10.20.1
last ip  : 10.10.20.254
broadcast: 10.10.20.255
netmask  : 255.255.255.0

That means I have a usable ip range from 10.10.20.1-.254 on this subnet.

would 10.10.20.0 be the default gateway for this subnet?