SSS: I can't understand this problem

[Nija]

Class= Cisco CCNA Semester 3
Chapter 6 - Access Control Lists.

Wildcard mask's are wupping me. I just can't understand them. I also had a huge problem with subnetting, but I eventually got around that (but it still takes me a while to do it, and I sooo can't do it without paper and pen)

Ugghhh..

So this is the problem:
1st take the ip 173.98.100.87 and break it into binary
2nd take the wildcard mask 0.0.0.255 and break it into binary
3rd compare which bits are checked (c) and which bits are ignored (i)

10101101.01100010.01100100.01010111
00000000.00000000.00000000.11111111
(this is the one that threw me)
cccccccc.cccccccc.cccccccc.iiiiiiii
or
0.0.0.255

Ugh that literally took me almost an hour.. and I'm not even sure it's right :bawl:

From then on, The chapter is assuming your a pro at this wildcard mask business. Ugh. I can't figure out what they want of me anymore. I tried taking the 11 question quiz at the end of the chapter and I got a 3 :bawl:

</rant>
thank you for your time.

[coleslaw]

I'm not so sure that you need to break it down into binary if you are only dealing with subnet values of 000 and 255.

The problem you mentioned is basically asking you to recognize all hosts belonging to x.x.x.87.

When comparing single bits, any bit of the subnet that contains a 1 masks the corresponding bit of the host IP, which means that you are only looking at those bits that are unmasked (subnet bit is 0).

But then again, what do I know about this stuff? I'm not an IT guy! :shrug: