Ok so I'm trying to understand ACLs (Access Control Lists) and I just somehow can't get it. Especially the part about the wildcards. any help???

What part of it do you not understand? I have to know this stuff also since I'm taking the CCNA exam soon, are you by any chance planning to take as well?.

 

Regarding wildcard, ACL uses a wildcard mask to define the portion of the IP address that should be examined. The wildcard mask's 0 and 1 bit specify the matching logic: 0 bit in the wildcard corresponds to address bit that must be compared while 1 bit instructs the router that the corresponding address bit do not need to be compared.

 

As an example:

 

Wildcard Mask: 0.0.0.0

Binary Version: 00000000.00000000.00000000.00000000

Meaning: Entire IP address must match

 

Example 2

 

Wildcard Mask: 255.255.255.255

Binary Version: 11111111.11111111.11111111.11111111

Meaning: Automatically considered to match

 

Example 3

 

Wildcard Mask: 0.0.0.15

Binary Version: 00000000.00000000.00000000.00001111

Meaning: First 28 bits must match

wow, thanks I actually get it now! And yeah, I'm in Comp. Network Engineering at my school, and I'm preparing to take the CCNA. Mostly I have trouble with the syntax of setting ACLs. such as in what order the terms go for a particlar ACL...