Help with wildcard masks
abefroman
Banned Posts: 278
in CCNA & CCENT
Does anyone have any tips for find wildcard masks? This is giving some trouble, especially when dealing with multiple c-blocks or multiple b-blocks.
Could someone post a method and a few examples?
TIA
Could someone post a method and a few examples?
TIA
Comments
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blackninja Member Posts: 385It's really easy to find the wild card mask, just flip the bits of the subnet mask;
subnet mask
255.255.255.0
11111111 11111111 11111111 00000000
wildcard mask
0.0.0.255
00000000 00000000 00000000 11111111
subnet mask
255.255.240.0
11111111 11111111 11110000 00000000
wildcard mask
0.0.15.255
00000000 00000000 00001111 11111111
or a trick is to minus the mask against 255:
255.255.240.0
255 - 255 = 0
255 - 255 = 0
255 - 240 = 15
255 - 0 = 255
0.0.15.255
SimplesCurrently studying:
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peanutnoggin Member Posts: 1,096 ■■■□□□□□□□blackninja wrote: »or a trick is to minus the mask against 255:
255.255.240.0
255 - 255 = 0
255 - 255 = 0
255 - 240 = 15
255 - 0 = 255
0.0.15.255
Subtracting the mask from all 255's is the easiest way in my opinion. Good explanation blackninja.We cannot have a superior democracy with an inferior education system!
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thehourman Member Posts: 723What exactly is wildcard mask?
As far as I know it is a amount of bits between subnet bits and host bits. Am I right?Studying:
Working on CCNA: Security. Start date: 12.28.10
Microsoft 70-640 - on hold (This is not taking me anywhere. I started this in October, and it is December now, I am still on page 221. WTH!)
Reading:
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steve514 Member Posts: 17 ■□□□□□□□□□A wildcard mask is the number of bits that indicate what part of an ip address can automatically assume any value. A wildcard mask is really just the subnet mask with the ones and zeros inverted to create the wildcard mask. An example of this would be a wildcard mask of 0.0.0.255, which corresponds to the subnet mask of 255.255.255.0. Hope this helps!
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thehourman Member Posts: 723So it is like changing all 1s into 0s and all 0s into 1s?Studying:
Working on CCNA: Security. Start date: 12.28.10
Microsoft 70-640 - on hold (This is not taking me anywhere. I started this in October, and it is December now, I am still on page 221. WTH!)
Reading:
Network Warrior - Currently at Part II
Reading IPv6 Essentials 2nd Edition - on hold