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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