OSPF wildcard mask

Found this in Odom's book
"The answer with wildcard mask 0.255.255.0 is illegal, because it represents more than one string of binary 0s separated by binary 1s."

It means that I can't mix 0 and 1 in a wildcard mask?
All 0 must be on the left side and all 1 on the right side or viceversa with no mixed 1 & 0?

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Comments

OfWolfAndMan

With the wildcard, once you see at least one binary 1, the remaining that follow should be 1.

example: to calculate a wildcard mask, say you have network 10.10.0.8 255.255.255.248. Take 255.255.255.255. Subtract your intended mask from that. Boom, you have 0.0.0.7

Deathmage

OfWolfAndMan wrote: »

With the wildcard, once you see at least one binary 1, the remaining that follow should be 1.

example: to calculate a wildcard mask, say you have network 10.10.0.8 255.255.255.248. Take 255.255.255.255. Subtract your intended mask from that. Boom, you have 0.0.0.7

...going to remember that for the exam! Koodos!