What is the use of a host mask/ wildcard with respect to subnetting and ranges?

Question

Taking the example of 10.0.0.0/20, that means my range is 10.0.0.0 to 10.0.15.255
I got that range because I know that the wild card is 0.0.15.255 and I just add it with the beginning address 10.0.0.0

Now, in the case of 198.51.100.223/21, I have a wildcard/ host mask of 0.0.7.255. How do I use this host mask to get my range? The first address is 198.51.100.223. Do I just add each of them up? The last octet now goes beyond 255 which is wrong. How does this have a range of 192.51.96.0 to 192.51.103.254 ?

This two-part answer explains all about IPv4 addressing and subnetting. — Ron Maupin, Jan 08 '21 at 03:03
Yes, I am reading it. It talks about this very example. It doesn't explain the exact use of 0.0.7.255 — Akram ElectroTech, Jan 08 '21 at 03:05
Wildcard masks are used in Cisco ACLs, and the next section of that answer actually talks about another use. — Ron Maupin, Jan 08 '21 at 03:06
But it doesn't answer my question with respect to the subnet range — Akram ElectroTech, Jan 08 '21 at 03:11
Sure it does. Reread and understand it. What happens if you add the host mask to the network address? The host range (except for /31 and /32 networks) is the network address plus one to the broadcast address minus one. It is all explained in that answer. Really, it is just simple binary math. — Ron Maupin, Jan 08 '21 at 03:21
That's the overall range right? I don't understand, like I am asking when I add host mask to 198.51.100.223 where I want the subnet to start from. Not starting from the network address. — Akram ElectroTech, Jan 08 '21 at 03:26
I'll read some more and try to figure it out where I'm going wrong — Akram ElectroTech, Jan 08 '21 at 03:28
The subnet cannot start from there. You need to look at it in binary. — Ron Maupin, Jan 08 '21 at 03:28
Host mask & subnet mask decides the length if ip adress ranges in subnet. — Sagar Uragonda, Jan 11 '21 at 16:26

What is the use of a host mask/ wildcard with respect to subnetting and ranges?

0 Answers0