Routing Table Tools

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show route

• show route, show ip route, show ipv4 route, or similar show route commands will output the active routing table
• output shows:
  • destination
  • gateway
  • AD/metric
  • interface
  • source of the route
    • identified as a letter code
      • C = connected, S = static, R = RIP, B = BGP, D = EIGRP, O = OSPF, etc.

show arp

• a router keeps a cache of IP address that have been resolved to MAC addresses via the Address Resolution Protocol (ARP)
• inspecting the ARP cache table is useful for discovering:
  • duplicate IP addresses
  • IP misconfigurations
  • routing protocol misconfigurations
• show arp or show ip arp to view ARP cache

route and ip route

The route command is used to view and modify the routing table of end system Windows and Linux hosts.

• routing table for an end system generally contains a single entry for the default route
  • is represented as the destination 0.0.0.0/0
  • any traffic that is not address to the local subnet is sent over this
• to show the routing table:
  • In Windows, run route print
  • In Linux,
    • route is part of deprecated package of tools
    • use ip route show and ip route add