So in this topic we will discuss about OSPF LSA types. OSPF is all about knowing its topology, complete topology and it relies a lot on the on the information that is generated by the link state advertisements and and that's how LS DB gets its information LS DB is the database that OSPF uses. So, there are different types of course, type 125 are the most types that we will be using. six types six to 11 are known as other types and and as mentioned, I mean they are not utilized within the within the network, but there are defined already within the database. So, there will be some certain cases that you will see type 678 910 911 type eight and nine is used by OSPF version three. Definitely we can do.

We can do a lab on that to verify the information on type eight and nine. But the main common ones is 125. So type one is the router LSA and these are the advertisements that are generated by by the routers within the same area. And, and the header of this type is basically advertised as a link state ID type one And it just tells the it just tells the neighboring devices about itself within the same area. Type two is the network LSA and the network LSA is are generated by the designated routers within that area. As you know, there will be if there's if there are like one, one or more routers in an area let's say two routers in an area then one will be the designated router.

The other one will be the backup designated router. So so the network LSA will be generated by the designated router. Okay, and the header will be advertised as link state ID type two LSA with the IP address of the of the Dr. router, type three LSA is on Known as the summary LSAT and as you know within one area there will be one which is which is ABR router and the router connects to different areas. So basically what it does it summarizes the information that it receives from one area and sends it as a summary to the next area. So, the header of this will be shown as the as the summary link advertisement and it will be like shown as a link state ID type three LSA with the designation or destination network number. Now, type four is a ASPR summary link and it informs the rest of the OSPF domain how to get to the ASPR.

As you know, it's br is basically the router that has one interface connected to the external routes. And that's how the internal domain OSPF know about the SPR because it advertises itself as type for advertise link. Type five is basically again, it's generated by the SPR. And it has all the information or the routes to all the external destinations of an autonomous system which is not within the OSPF domain. And the link state ID of this type will be type five LSA and it is going to have the network number of the external routes. So I hope this was informative and the next topics that we will be bringing is all About labs and we will go through some topologies and build the link state LS DB and go through the information step by step and and then do some testings