If you’ve been doing Networking, then you are probably familiar with CIDR notation, and how it correlates to Subnet Masks and Wildcard Masks. Which means you know that a
/26 correlates to a Subnet Mask of
255.255.255.192 and a Wildcard Mask of
But what is the purpose of a Wildcard Mask if you already have Subnet Masks that largely do the same thing? That is a good question. And the answer to that is they allow Discontiguous Wildcard Masks.
Subnet Masks can only identify sequential IP addresses. Wildcard Masks, however, can identify IP addresses which are not sequential.
This video talks through what that means, how that works, and illustrates combining 8 different non-sequential /24 networks using a single Wildcard mask.
- Basic definition of Wildcard Masks
- Basic definition of Discontiguous Wildcard Masks
- Topology explanation
- How an Access Control List (ACL) matches traffic
- Theory behind a Discontiguous Wildcard Mask
- Viewer Quiz – Find where else Discontiguous Wildcard Mask can be used
- Why do Discontiguous Wildcard Mask exists?
- Why Discontiguous Wildcard Masks are rarely used today
- Regular Wildcard Mask are still used today
A pre-cursor to this video is the video I created recently that defines Wildcard Masks themselves.