Tag Archives: ccnp route

On demand routing (ODR)

1. Must turn on CDP for all routers; hence this routing protocol is Cisco proprietary. 2. Only works in hub and spoke topology. 3. Has a default administrative distance of 160. 4. Extremely easy to configure. 5. Makes default route … Continue reading

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Type 10 LSA – Opaque LSA

This LSA is an extension of OSPF. The extension is for doing OSPF traffic engineering. MAX-LSA – Protects against adjacent router’s excessive LSA in the OSPF domain. Excessive LSA will cost router’s high cpu resources. This is to limit the … Continue reading

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LSA types

1. Router LSA – This LSA is produced by every router. The LSA contains information of the router’s connected interfaces, states, neighbour router type, any known ospf routers connected to the router’s link and outgoing cost of each link. This … Continue reading

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Building OSPF adjacency

Database Description Packet (DDP) – This contains the summary of all the LSAs, it only contains the headers and not the complete LSA. This allows router to see if its own link state database is updated. This is type 2 … Continue reading

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OSPF finite state machine

Reference: Routing TCP/IP 2nd Edition Jeff Doyle, page 353-357. OSPF router goes through several states before adjacency is formed. DOWN – No hello packets was seen from the neighbour router since the last dead interval. If an OSPF router goes … Continue reading

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Understanding OSPF

Open Shortest Path First is using Djikstra’s shortest path first algorithm. It is a link-state routing protocol, another link-state routing protocol is Intermediate System to Intermediate System also known as IS-IS. General facts about OSPF 1. Uses its own transport … Continue reading

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Routing table – a router’s decision

How router chooses a route. A router that has multiple exit to a destined network will decide which route will be in routing table by these: 1st: Choose the route that has the longest prefix match. 2nd: Choose the route … Continue reading

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