Sunday, February 1, 2015

Cisco CCNP - 300-101 - Route Redistribution

So it's that time again for me to renew my Cisco Certifications. As a result, this post will be based on my preparation for the CCNP Route Exam (300-101).
In this post I will be focusing on Route Redistribution

Route Redistribution
    - Used to take route learned from one routing protocol and inject it into another
    - Can be done within the same protocol where different autonomous numbers are used
    - must have at a minimum 1 physical interface in each domain
    - Uses the "redistribute" command with options
        - protocol - the source routing protocol
        - process-id - for routing protocols which uses process id
        - metric - include bandwidth, delay, etc
        - match - matches internal OSPF routes
        - tag - unitless integer to redistributed routes
        - route-map - used for logic in the referenced route map
    - Only information in the routing table is used
    - Redistributed routes are treated as external routes
Redistributing EIGRP into OSPF and vice versa
    - OSPF creates a type 5 LSA to represent each route
    - Type 7 used when redistributed into a not-so-stubby area (NSSA)
    - OSPF uses an integer metric
    - Route filtering and route summarization can be used at the redistribution router
    - when redistributing OSPF into EIGRP the metric must be set using either of:
        - default-metric
        - metric
        - route-map
        - Can use "redistribute ospf 1 metric 10000 33 255 1 1500"
    - External routes are flagged with EX
    - OSPF has its own default metric for redistributing EIGRP routes
    - OSPF external routes are either type 1 (E1) or type 2 (E2)
    - By default OSPF create type 2 (E2) when redistributing
E1 vs E2 routes
    - E2 routes uses external cost only
    - E1 routes uses both internal and external cost
    - OSPF prefers E1 over E2 when given a prefix/length
When Route Redistribution is not possible?
    -    Stubby and totally stubby areas cannot do redistribute external routes

CCNP official Cert Guide - CCNP Routing and Switching - Route 300-101

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