Packet tracer labs with ospf
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The function of the DR is to distribute updates to the other routers connected on the multi-access network. On multi-access networks such as Ethernet or frame relay point-to-multipoint, a Designated router and potentially backup designated router is elected. OSPF uses a centralized management method of distributing route updates on networks. In OSPF, you can only summarize routes at an ABR/ASBR on the link facing the inbound towards the network. OSPF uses the destination addresses 225.0.0.5 for all OSPF routers and 224.0.0.6 for communication between the DR/BDR (Designated Router and Backup Designated Router). OSPF sends multicast traffic packets have a TTL of 1 so they never travel further then 1 hop.
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OSPF does not use TCP/UDP to encapsulate its traffic but instead encapsulates the traffic into its own protocol protocol number 89. These routers connect OSPF to an external network such as the internet or a redistributed autonomous system. Any routers that connect an area to an external autonomous system are called Autonomous System Boundary Router(s), (ASBR’s). Routers that have these connections to Area 0 are called Area Boarder Router(s) (ABR’s). All area’s must have a single interface attaching the area to area 0. All traffic destined between areas, also known as inter-area traffic must traverse area 0 which is called the backbone area. OSPF was designed to support Variable Length Subnet Masking (VLSM) and a hierarchical network model by nature. Many factors can take into play to manipulate the “best path” such as a distribute list, route maps or policy based routing. Just because a backbone router knows about the link does not necessary mean the router will use that link in the routing table. OSPF is a link state protocol and each router maintains a topology map of their configured area however routers in Area 0 maintain the topology for the entire network, in which case backbone routers know of every single link and route. So with all that being said lets take a dive into the technological pool of OSPF… Meaning that there are books dedicated to OSPF design, implementation and configuration with 500+ pages but for the CCNA you’ll just need to know the basics which include in summary single and multi-area configuration, link priority, DR/BDR Election, OSPF network types, stub area types, timers, default route propagation, route summarization and Link State Advertisements (LSA) Types. However in general, OSPF is a very large technological and configurational protocol. So what makes OSPF so special? It’s really the functionality and the hierarchical nature of the protocol in which it fits perfectly with modern networks. OSPF is the industry standard in internal dynamic routing protocols and it’s supported on nearly all vendor platforms.
#Packet tracer labs with ospf free
Free CCNA Workbook has saved the best for last. If you’ve completed the labs in the Free CCNA Workbook up until this point then boy you’re in for a real treat.