In order for OSPF to keep its topology current and up to date with any changes or failures, it has some important timers. Three timers I am going to talk about today are the hello interval timer, dead interval timer, and the retransmission timer.  Hello Timer- The hello timer is a timer that dictates how…

Today I am going to dive into OSPF router adjacency roles. In broadcast/non-broadcast multi-access network topologies, OSPF elects routers to maintain a certain role within the topology to provide redundancy, and make communication/updates more efficient. The roles that make OSPF broadcast network types run smoothly are the DR (Designated Router), BDR (Backup Designated Router), and…

Today I am going to talk about OSPF neighbor states and what goes on under the hood when a new OSPF topology first comes online. Before a link reaches a full state and the network is fully converged with a complete identical topology map. For broadcast and non-broadcast multi-access topologies, link neighbors must go through…

Today I am going to talk about the types of messages that can be sent when OSPF is enabled. Every message type is unique in its own way and allows OSPF to function as smoothly as it does. These message types each serve their purpose in their own way from discovering neighbors to providing reliability….

Hi, today I am going to talk about OSPF routers and the role of each router. Since OSPF is a vast protocol with a lot going on, different routers carry different duties to make sure that the OSPF AS functions the way that it is supposed to. Without these routers and their role OSPF would…

Today I am going to begin to talk about OSPF and OSPF areas. OSPF is short for Open Shortest Path First, and is an IGP link-state protocol. OSPF operates with routers all having the same identical topology map and from that identical map, every router calculates the shortest path possible using Dijkstra’s algorithm. The shortest…

Today I am going to talk about floating static routes. Floating static routes are backup routes that are strategically configured on a router that serves as a redundancy mechanism in case a primary dynamic route fails. These static routes are invisible to the eye, meaning when they are configured if you look at the routing…

Today I am going to be talking about EIGRP which stands for Enhanced Interior Gateway Protocol. EIGRP is an dynamic IGP that is an advanced distance-vector protocol. EIGRP is viewed as a “hybrid” protocol because it has features of both distance-vector and link-state protocols. EIGRP has an AD of 90 and uses a composite metric…

Today I am going to talk about RIP which is Routing Information Protocol. This is a dynamic protocol and is mostly obsolete because there are other protocols that converge much more quickly like OSPF and EIGRP. RIP has a 30 second update timer and a 180 second invalid timer making convergence very slow compared to…

Today we are going to talk about AD and metrics. If you’ve ever seen a routing table you’ve probably seen something like this [110/65]. Here’s a picture of it below: AD- The number to the left is AD which stands for administrative distance and the number to the right stands for metrics. Ever wondered when…