Wildcard misunderstanding

[TheGoob]

Hello

I have done best I can in terms of research on what Wildcards are but I just am not processing it.

Do Wildcards work to create a range? For example, would 192.168.1.0 0.0.0.15 mean 192.168.1.1 - 192.168.1.15? 

I want to break up 1 Network onto 2 PBR's. 

192.168.1.1 - 192.168.1.64 but it is asking for a Wildcard, and I am just not understanding! Would it be 0.0.0.64? I then want 192.168.1.65 - 192.168.1.128, would that be 0.0.0.128

I see so many examples but I just don't understand. 

[David Ruess · Accepted solution]

Its basically the inverted subent mask. So in your example of:

192.168.1.1 - 192.168.1.64 - your subnet mask is 255.255.255.192

The wilcard is (255.255.255.255 - 255.255.255.192) Which is 0.0.0.63 - you are subtracting each decimal value from 255 which is the max in a mask

It will take any IP in that "range" and match it against what you're trying to do

I used this subnet calculator to help you out:

https://www.calculator.net/ip-subnet-calculator.html?cclass=any&csubnet=26&cip=192.168.1.0&ctype=ipv4&printit=0&x=73&y=18

Check out this page as well:

https://en.wikipedia.org/wiki/Wildcard_mask

[Jon Marshall · Accepted solution]

A wildcard is the inverse of a subnet mask (usually but it doesn't have to be). 

So you want two subnets - 

192.168.1.0 255.255.255.192 (which covers 192.168.1.1 -> 192.168.1.62 with broadcast 192.168.1.63) 

192.168.1.64 255.255.255.192 (which covers 192.168.1.65 -> 192.168.1.126 with broadcast 192.168.1.127)

in the above subnet mask is the same for both subnets and the wildcard would be the same for both subnets as well. 

The wildcard you would use for both subnets would be - 0.0.0.63   which is the inverse of 255.255.255.192. 

You really need to do it in binary but you basically turn all the bits off that are on in the subnet mask and on if they are off in the subnet mask eg.  each octet has 8 bits with these values - 

128 64 32 16 8 4 2 1

so 255 would be all the bits on ie. 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1 = 255 and to get the wildcard equivalent turn them all off which = 0. 

For the last octet 192 that would be 128 + 64 = 192  in the subnet mask so the first two bits are on and the last six are off so to get the wildcard value you turn those two bits off and turn the rest on ie. 32 + 16 + 8 + 4 + 2 + 1 which equals 63. 

If you want the shortcut then to get the equivalent wildcard value just subtract the subnet mask value from 255 so - 

255.255.255.192 = 0.0.0.63 

255 - 255 = 0 (for the first 3 octets) and 255 - 192 = 63 for the last octet. 

Jon

[TheGoob]

Wow. You both explained it amazingly clear and it actually clicks. I need to delve into it more but I am absolutely better off now than I was. It was the formula I was missing, and my mind couldn't wrap around the answer without knowing the how.

How do I accept both as a solution?!

[Jon Marshall]

Not really sure but think you can accept both as solutions if that is what you want.

Jon