• Joins two or more networks
  • Passes packets from one network to another
  • Can do the following:
    • Connect dissimilar networks (LANs and WANs)
    • Interpret layer 3 (network layer) and layer 4 (transport layer) addressing
    • Determine the best path for data to follow from point A to point B
    • Reroute traffic if the path of first choice is down but another path is available
  • May perform any of the following:
    • Filter broadcast transmissions
    • Prevent certain types of traffic from getting to a network
    • Support local/remote connectivity simultaneously
    • Provide high network fault tolerance through redundant components
      • Such as power supplies
    • Monitor network traffic and report stats
    • Diagnose internal connectivity problems and trigger alarms
  • Act as a broadcast boundary
    • Don't forward broadcast traffic

Routing Table

Routers and routing tables

  • Database maintaining information about where hosts are located and the most efficient way to reach them
    • Routers rely on them to identify which router is the next hop to reach a particular destination host
  • Contain IP addresses and network masks that identify a network that a host or another router belongs to

Routing Path Types

  • Static routing
    • Network admins configure a routing table to direct messages along specific paths
  • Dynamic routing
    • Automatically calculated paths between two networks
    • Maintains information in a routing table
    • Router can detect problems with failed/congested routes and reroutes messages through a different path

Optimal Paths

  • Routing protocols
    • Used by routers to communicate with each other to determine the best path
  • Routers rate reliability and priority of a routing protocol's data based on:
    • Administrative distance (AD)
      • Number indicating protocol's reliability
    • Convergence time
      • Time it takes to recognize a best path in event of a change or outage
    • Overhead
      • Burden places on underlying network to support the protocol

Networking Computer Science