Routing table entries will be filled in statically by network administrator or will be filled in dynamically with the help of routing protocols. Router table will have destination IP address,next hop and router port interface. There are different types of routers viz. These routers use different protocols and algorithms to build the routing table. RIP determines optimal route for the packet to reach destination by hop count.
The maximum hop count is RIP protocol updates the network constantly. The updates are always broadcasted. RIP V1 — It is a classful routing protocol. It does not support authentication of update messages. RIP V2 — It is a classless routing protocol. It sends updates as multicasts. To enhance the growth and ease of management OSPF divides network and routers into subsets and areas. OSPF involves type of service routing which means multiple routes can be installed according to the priority or type of service.
Routing is done by sustaining the database with link state information in the routers and route the weight computed using link state and IP address.
To update the database the link states are transmitted from autonomous system to routers. After that, on the basis of the information stored in the database, each routers build shortest path tree as a root node.
OSPF enables the authentication mechanism, it offers two type of authentication methods namely MD5 algorithm and simple password. OSPF supports subnet specific, classless routes, classfull network specific routes and hosts. Routing Information Protocol is the straight implementation of distance vector routing for local networks. In every 30 seconds, it delivers an entire routing table to all active interfaces.
Hop count is the only metrics to describe the best path to a remote network, but it can be 15 at max. It prevents routing loops, through restricting the number of hop counts permitted in the path. Convergence is a process of collecting the topological information or updating the information for the other routers through the implemented routing protocol. Convergence occurs when the router is transitioned from either to forwarding or blocking states, and it prevents data forwarding at that instant.
The main issue with convergence is the time it takes to update information in a device. Slow convergence can result in inconsistent routing table and routing loops. Routing loops forms when routing information is not updated or the when the information propagated throughout the network is wrong. Split horizons and route poisoning is the solution to the routing loop problem.
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