The following will describe what you need to know about routers in order to pass the ICND1 Exam.
- Routing forwards data packets using a layer 3 device
- Routers expand the scalability of networks
- Routers determine the best path for transmitting data
- Routers have two key functions: 1) Path determination 2) packet forwarding
- Paths have: Speed, Latency, Media Type
- In order to select the best path, routers use: 1) Static routing 2) Dynamic Routing, 3) Default Routing
- Administrative Distance is used to weigh or determine the best path (lower the better).
- Routing tables – store information about network paths
- Routing updates – Routers talk to each other about the status of their routing tables
- Directly Connected – Administrative Distance is 0; The network interface is directly attached to the network
- Static Routes – Administrative Distance is 1; Routes are manually configured
- Dynamic Routes – Learned by the router
- Convergence time – The time it takes for a router to learn about changes.
- Default Route – Used when no other route can be found
- Common metrics for routing protocols: 1) Bandwidth 2) Delay 3) Hop Count 4) Cost
- Distance Vector – only cares about the direction and hop count and does not need to know the path to every network. Sends periodic updates to their neighbors. “Routing by Rumor”
- Link-State Routing – Builds an internal map of the network topology, sends updates when changes occur, link state refreshes at long intervals
- SPF – Shortest Path First
- EIGRP – Combines distance vector and linked state routing
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