10.0.0.3/8 is bad mask but 10.0.0.2 is not?

[hfakoor222]

On switch LS I create 10.0.0.1/8

on D2 I create 10.0.0.2/8

as part of a lab

I accidentally type in 10.0.0.3 and it says bad mask (see out put below)

I thought numbers went up to 255 so why is 10.0.0.3 a bad mask?

Toplogy below:

Output from the right switch, on int vlan 1:  

[hfakoor222]

I recognize I mis-applied a /8 prefix using .252, but I still want to know why the 252 doesn't work 

[balaji.bandi · Accepted solution]

because 10.0.0.3 is broadcast IP if you use /30.

0 - network and .3 broadcast, you can only use 2 usable ip that is 1 and 2

good video to start ipv4 subnet, if you have not done so.

https://www.youtube.com/watch?v=UCoVs1Ri1IA