How to Build an OSPF Network

Network Architect, Marc Perea, walks through how to build an OSPF Network. Learn how to document your network before you start creating it, and then how to configure and organize your routers for an efficient OSPF Network. Watch parts 1 and 2, and follow along with the written instructions below.

Video: How to Build an OSPF Network – Part 1 #

Video: How to Build an OSPF Network – Part 2 #

Step-by-Step Guide #

Part 1: Visualize & Diagram Your Network #

1. Create a blank diagram using your favorite diagramming tool (Vizio, Lucidchart, Diagrams.net, etc)
2. Insert router icons and create a basic layout of your network by organizing them and linking them with lines
3. Insert an internet icon at the top of the diagram
4. Choose an IP range for your transport IP’s and document it on a blank section of your diagram – I.E. 100.64.0.0/10 (CGNAT)
   1. This is the network that communicates with OSPF and is different from your internet IP’s
   2. This means Private IP’s can be used to help conserve Public IP’s – but you can use Public IP’s if you want.
5. Assign a range for your Loopback IP’s, which will also be your Router ID’s, and document it under your IP range – I.E. 100.127.0.0/24
6. Assign a range for your transport network – I.E. 100.126.0.0/26
7. Subnet all of your links, starting closest to the internet* – I.E. 100.126.0.0/29
   1. Increase by your subnet as you go – In this example, a /29 – I.E. 100.126.0.8/29, 100.126.0.16/29
   2. *This pattern is arbitrary, organize and flow your link subnets however it makes sense to you.
   3. Need help with subnetting? Check out this tutorial! – NEED LINK
   4. Pro-Tip: Use /29 instead of /30 to help with troubleshooting by allowing you to have more than 2 hosts on the subnet. This allows extra devices that can take a Layer 3 IP to be added, so if you are having network trouble you can take a look at your ARP, Bridge, and Mac tables to determine if you are having a link problem or a router problem.
8. Starting closest to the internet*, assign your hosts an IP – I.E. .1 & .2 for your 100.126.0.0/29 link
   1. Continue assigning hosts with IP’s – I.E. .9 & .10 for 100.126.0.8/29
   2. *This pattern is arbitrary, organize and flow your host IP’s however it makes sense to you.
9. Assign a Loopback/RID to each router – I.E. 100.127.0.1/32, 100.127.0.2/32
   1. Since this is just a Loopback IP, the subnet is /32
10. (From Part 2 Video) Assign physical ports to your routers.
    1. A good practice is to assign ether1 to all upstream connections, having it be the closest internet facing Ethernet port
11. Your diagram is now all set!

Part 2: Configure & Organize Your Network #

• Fill out once Video CC is done