Open Shortest Path First $($OSPF$)$ is a popular dynamic routing protocol that was first standardized in $1989.$ Being an open standard, most types of routers support OSPF, and it is widely used in large enterprise networks. OSPF uses a link$-$state routing $($LSR$)$ algorithm and is an interior gateway protocol $($IGP$).$ Routers using OSPF communicate with each other with link$-$state advertisements $($LSAs$)$ that are stored in link$-$state databases $($LSD$).$ OSPF supports Variable Length Subnet Mask $($VLSM$),$ converges quickly, and uses the concepts of areas.