MicroNugget: What are IPv4 Wildcard Masks?

In this video, Keith Barker covers Wildcard Masks: what they do, how they do it, and in what situations you should employ this tool. This allows you to tell an access list entry that you’re concerned about identifying a single subnet on a remote network.

Computing is all about specificity, but sometimes you don’t need to outline every single aspect of a particular feature. A Wildcard Mask’s responsibility is to identify some components of an IP address that you don’t care about and then apply policies to them based on values you didn’t explicitly specify. For example, let’s say you’re going to deny any traffic sourced from the 172.16.56.0 network. You’ll need to create an access control list, but if you’re dealing with a 24-bit network, you’re looking at 254 distinct possibilities. You want to write the policy so that you discriminate against IP addresses based on the first three values, but don’t care about the last one. That’s where a Wildcard Mask comes into play.

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[KeithBarker]

Yes, that is a correct way of looking at it. Good work.

Keith

[fahad]

Whenever I watch a Keith Barker video, I press like first then watch the video.

Thanks Keith.

Awesome Stuff.

[benjeee]

My guy, this is the best explanation ever

[Mileumavozess]

A aula mais clara que eu já vi desse assunto na minha vida, muito obrigado, um dia meu CCNA sai

[bitwamet]

Keith can u explain how this wild card works 0.128.0.16

[tenzingsherpa]

Keith is the best ## Better than my university teacher

[TheMirrorYouDeserve]

But why is it a 10, do you have more axamples?

[DerpyNetworking]

The question is why is it different than a regular subnet mask? The bit meanings are flipped. What was the decision behind this?

[lekulahowangahaora]

I am still onfused how to work with those 0 Sir?

[surferdjnj]

Am I correct that with a SNM bit that are on mean LOOK. But with a Wildcard Mask bit in the on position mean DONT look, AKA Variable?

[lashatt]

why are used wildcard mask in ACL and why not used usual subnet mask in ACL ???

[not_legal]

lol Keith I don't get it anyway)))

[neumei]

It would be a great video Keith, except I DONT CARE!! ; )

Thanks for the detailed description. And god damn can you code! I guess that kinda comes with being CCIE...

Rock on.

[lightningvini]

this guy doesn't like air fresheners!