From the course: Learning Subnetting
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Classless Interdomain Routing (CIDR)
From the course: Learning Subnetting
Classless Interdomain Routing (CIDR)
- [Instructor] In this video, we want to discuss a term that gets misused oftentimes. It's CIDR, C-I-D-R, which stands for Classless Inter-Domain Routing. A lot of times, people equate CIDR to subnetting. It's really the opposite, in fact it's not subnetting, it's supernetting. With subnetting, we're adding bits to a default subnet mask, but with supernetting, we're removing bits from the default subnet mask. Why would we want to do such a thing? Well if we're an internet service provider and we're advertising thousands and thousands of routes between routers, it might be more efficient if we could summarize a block of those routes. And that summarization is possible thanks to CIDR. Consider this example. We've got four network addresses, and here's what those network addresses look like in binary, and we know we're dealing with a class C network because the first octet is 192 for each of the networks, and these are each networks that a router might be advertising, however what if we…
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