Wildcard mask Can someone check this questions

Hi,

This doesn't look right to me. Here is the question.

You have an IP address and wildcard mask of 10.0.20.5 255.255.0.0. Which of the following IP addresses are affected by this rule? (Choose 2 )

1) 10.0.0.10
2) 192.168.20.5
3) 10.2.1.1
4) 172.30.20.5

If I thought the question was in the right format I would have chosen 1 and 3 to be the answers, but Sybex 5 states you can't have a wildcard mask in this format ( 255.255.0.0 ) in other words the values that need to be matched must come first like this ( 0.0.0.255 or 0.255.255.255 etc..).

The answers for the above question was 2 and 4. If this is right Sybex 5 was wrong do you guys agree on this ?

Thanks in advance.

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Comments

Megadeth4168

I think 2 and 4 are the correct answers. If this means Sybex is wrong I wouldnt be surprised... I caught a few errors in their Network+ book I studied from.

Longbow

2 and 4 are correct because the wildcard mask dictates that the 3rd and 4th octets exactly match the 3rd and 4th octets of the address 10.0.20.5 which is 20.5. Only 2 and 4 contain these values.

KGhaleon

The question is vague since it doesn't specify if your looking for denied or permitted addresses, but it assumes you know that all addresses are normally denied and that the only ones affected by the wildcard mask are 2 and 4.

KG

Longbow

I agree, KGhaleon, this is confusing - and very much in keeping with the actual flavor of Ciso test questions (in my opinion).

Sa'ad

Thanks for your quick responses fellaz, that helped clarify things.