{"id":276,"date":"2014-10-06T21:18:26","date_gmt":"2014-10-06T21:18:26","guid":{"rendered":"https:\/\/learncisco.net\/index.php\/link-state-databases\/"},"modified":"2023-01-27T19:17:46","modified_gmt":"2023-01-27T12:17:46","slug":"link-state-databases","status":"publish","type":"page","link":"https:\/\/www.learncisco.net\/courses\/icnd-2\/an-overview-of-ospf\/link-state-databases.html","title":{"rendered":"OSPF Neighbor States and Link-State Database"},"content":{"rendered":"

This is the convergent process that we’re looking at right now. We’re also going to see the neighborship formation process. \u0422his is in fact a subset of. But let’s say we’ve got some information dealt between two routers. One rather has more information than another. We got to get that information across to the other side, synchronize those routers databases, if you will. This would be the process.<\/span><\/p>\n

 <\/p>\n

\"OSPF<\/p>\n

First, we would have had to do some of the initial steps of neighborship formation, we do that with hellos. Then we send a database descriptor packet, DBD, okay that acronym is right here on this page. That’s our Type 2 Open Shortest Path First, or OSPF, packet type. And that lists off all the things we don’t know about. How do I ask for those things? Oh! And by the way, it’s acknowledged, you can see that. But how do we ask for those things that we glean from the DBD that we don’t have yet?<\/p>\n

We send out our link-state request and you can see here that it’s asking for a specific entry. It’s not asking for everything. No just what it needs. In this case, it needs a specific entry for the 172.16.1.0\/24. The router that receives that link-state request has to send a link-state update back. Oh, here is the information I have for that network you’re looking for. And notice at the bottom, we’re polite, we say thanks. We send that link-state acknowledgment back, so that way there they know we receive that particular entry we had asked for.<\/p>\n

OSPF Neighbor States<\/h2>\n

In the world of examinations, there are some bullets that you have to bite in terms of memorization. Make sure that you’re in the clear on this important memorization that you see here. And here are the states.<\/p>\n

\"OSPF<\/p>\n

We have, in fact, seen two of these states before, the Two-way state and the Full state. We didn’t see it, but we were talking about it. So I want you to be able to rattle off those states in your head. Can I do it myself? I’m going to do it:<\/span><\/p>\n