packets
packets
**used to announce new OSPF information and to reply to certain types of requests
The default duration of the OSPF dead timer is four times longer than the OSPF hello timer. Typically, the hello timer is set to 10 seconds, which means the dead timer defaults to 40 seconds. This ratio helps ensure that OSPF routers have sufficient time to detect a neighbor's failure before declaring it down.
hello packets
In OSPF, a topology database is a data structure that each router maintains to store information about the network topology within an OSPF area. It includes details such as the network links, their costs, and the routers connected to those links. This database is used to calculate the best routes for routing packets through the network.
To build OSPF and ISIS adjacencies. To verify that packets arriving at the router are allowed by any configured firewall filters.
OSPF (Open Shortest Path First) uses the Dijkstra algorithm, also known as the Shortest Path First (SPF) algorithm, to populate its routing table. It builds a link-state database (LSDB) that contains information about all the routers and their links within the OSPF area. By calculating the shortest path to each destination based on the cost of the links, OSPF determines the optimal routes for data packets. This allows OSPF to efficiently update its routing table and optimize network traffic.
The first step OSPF and IS-IS routers take in building a shortest path first database is to exchange link-state advertisements (LSAs) or link-state packets (LSPs) with neighboring routers. These packets contain information about the router's directly connected neighbors and the state of their links.
dead time and hello time
routing protocol: helps to find the best path to transfer the packets from one network to diffrent network example: rip: routing information protocol igrp, ospf...... routed protocol: helps to carry the packets to the destination. example: smtp : transfer the mails ftp : transfer the files.
OSPF LSA throttling helps the dampening of LSA updates in OSPF during times of network instability.
OSPF uses cost as its routing metric . cost is calculated for every outgoing interface of a router through which packets transfer. it is calculated by the formula cost = 100000000/(bandwidth of output interface) most likely bandwidth of serial int is 1544kb= 1544000 bytes PS: all cost calculation to be done in bytes for ease