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CCNA 3.8.a: Default route

Overview:

A default route is used to route traffic to any network that is not in your routing table.

Without a default route defined, any traffic destined to a network that is not in the routing table will be dropped by the router.

 

Study Notes:

  • A default route is configured to route packets to networks that are not in your routing table
  • Without a default route, the destination address must match an address in your routing table, otherwise the packets will be dropped by the router
  • Typically, the default route points to the internet
  • A default route puts the onus of routing on the next hop router.
  • Most often the default route is an upstream router.
  • It's like a router saying I don't know how to get to that destination, but my default route says to send it to this next hop so I'll make it that router's job to figure it out.
  • A default route identifies the gateway IP address to which the router sends all IP packets for which it does not have a learned or static route.
  • A default static route is simply a static route with 0.0.0.0/0 as the destination IP address.
  • Routes that identify a specific destination take precedence over the default route.
  • Configure an IPv4 default route by typing:
config t
    ip route 0.0.0.0 0.0.0.0 <exit-interface-on-this-router>
    --OR--
    ip route 0.0.0.0 0.0.0.0 <next-hops-ipv4-address>
  • Configure an IPv6 default route by typing:
config t
    ipv6 route ::/0 <exit-interface-on-this-router>
    --OR--
    ipv6 route ::/0 <next-hop-ipv6-address>

Labs:

PacketTracer Lab: CCNA-3.8.a-Default-route.pkt

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