0

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 ?

Akram ElectroTech
  • 43
  • 6
  • 1
    [This two-part answer](https://networkengineering.stackexchange.com/a/53994/8499) 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
  • 1
    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

0 Answers0