CCNP Exam Prep Tips and Must Knows

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Things You’ll Need to Know about Route Redistribution:

Configuring a Distribute List

  • Define the traffic filtering or permit or deny routes using:
    • Access List
    • Route Map
  • Configure a Distribute List to use he ACL or route map
    • Apply to inbound or outbound updates

Configuring a Prefix List

  • Prefix lists match routes in part of an address space with a subnet mask that is longer or shorter than a set number
  • For example:  R(config)#  ip prefix-list Test permit 10.8.0.0/16 le 22

Configuring a Route Map

  • Route maps are complex access lists that allow conditions to be tested against a packet or route using the match command
  • If the conditions match, actions can be taken to modify attributes of the packet or route.  These actions are specified by the set commands
  • For example: 
  • R(config)# route-map MYROUTEMAP permit 10
  • R(config-route-map)# match ip address prefix-list Test
  • R(config-route-map)# set interface Ethernet 0/0

Route Redistribution

  • Routes learned by another routing protocol, static routes or directly connected routes can be redistributed into a routing protocol. For example:  EIGRP learned routes can be redistributed into the OSPF process
  • Only routes learned by the router itself are redistributed

Seed Metrics

  • Initial, or seed, metric for a route is derived from the directly connected router interface
  • Default-metric command can be used to establish the seed metric for the routes or the metric can be specified when redistributing (e.g. via a route map)

Default Seed Metrics

  • RIP – Infinity
  • EIGRP – Infinity
  • OSPF – 20 (except for BGP which is 1)
  • BGP – BGP metric set it IGP metric value

Make sure you can configure:

  • Route redistribution for all routing protocols
  • One way redistribution with static route or default route
  • Two way redistribution with route filtering
  • Distribute Lists
  • Prefix Lists
  • Route Maps
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