OSPF

+ 224.0.0.6 (All Designated Routers) : Designated Router (DR) and Backup Designated Router (BDR). It is utilized to optimize communication between the DR and BDR, and regular OSPF routers do not receive messages from this address.

From DALL-E with Some prompting
The image is a visual representation of the operation of the OSPF (Open Shortest Path First) protocol. Here is the interpretation of each step depicted in the image:

get LS (Link State): OSPF routers collect cost values from all physically connected routers. This step involves determining the adjacency relationships between routers and the state of each link.

LSA (Link State Advertisement): Each router creates an LSA that contains its link-state information and disseminates it to other routers within the network. During this process, the multicast address 224.0.0.5 is used to broadcast the information to all OSPF routers.

LSDB (Link State Database): The information from the received LSAs is compiled into the LSDB of every OSPF router. This database should be identical across all routers within the Autonomous System (AS) and contains the complete topology information of the network.

Shortest Path Tree Calculation: Using the LSDB, each router calculates the shortest path tree from itself to all other destinations employing the Dijkstra algorithm. This calculation aids each router in determining the optimal routing paths.

Routing Table Update: The shortest path information calculated is then used to update the routing table of each router. This enables routers to forward packets using the optimal routes.

At the bottom, there’s a section titled Dynamic Updates, indicating that when there are changes in the network topology, new LSAs are generated and propagated through the network. This ensures that all routers’ LSDBs are updated and, as a result, the routing tables are also updated to reflect the new optimal routes.

In the top-right corner, it states “224.0.0.5 Broadcast IP for all OSPF router”, which indicates the multicast address used by all OSPF routers to receive LSA broadcasts.

This diagram provides a visual explanation of the core routing processes of OSPF, highlighting the mechanisms that enable efficient routing within the network and facilitate rapid convergence.