What is OSPF and How Does It Work?

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In this video, Keith Barker covers OSPF, the protocol that makes it possible for your routers to forward traffic all the way through your network. There are a lot of different topics to deal with when you break down OSPF, but Keith covers them with easy examples and simple demonstrations:

Start off with a sample network topology to visualize how OSPF works on it

Breaking down how LSAs make OSPF possible

How Link State Databases provide routers with all the network information they need

OSPF Hello messages and how they help routers share data

Visualizing the sort of network that OSPF would be useful for can help understand exactly how it does that. Keith starts with a sample network topology and splits it into areas. Different routers provide access to different areas, and eventually they'll become OSPF neighbors.

But before you get to that, it's important to understand Link State Advertisements (LSA). When you have a network topology with multiple zones, the connecting routers are responsible for creating an LSA and broadcasting them. LSAs contain all the information about the networks that each router services.

With OSPF, it's possible for routers to "meet" one another, send "hello"s to one another and share their link state information. Link State Databases are shared between OSPF routers, and in turn those routers leverage the data inside those databases to make decisions about routing data across the entire network.

OSPF is the language that makes it possible for all the routers across a network to collaborate like this. It also makes it possible to carve the network up into smaller chunks so that you don't have to create routing tables for every last destination in the network on every single router.

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