CCIE RS – Routing Concepts – Implement, optimize and troubleshoot redistribution between any routing protocol

Implement, Optimize and Troubleshoot Redistribution between any Routing Protocol

Redistributing Routing Protocols

I will briefly describe how redistribution works for each of the protocols. The best way to truly understand this is to lab up the scenarios and see what happens


RIP

RIP uses a hop count as it’s metric for routes, 16 being unreachable. You’ll want the metric to be defined in a way that will not allow for a routing loop to occur. A metric must be defined when redistibuting other protocols into RIP

router rip
network 10.2.0.0
redistribute static
redistribute eigrp[metric]
redistribute ospf[metric] 
redistribute isis 
default-metric [metric]

 


EIGRP

EIGRP uses a composite metric can can be computed based on: bandwidth, load, delay, reliability and MTU. A metric must be defined when redisitrubtuing other routing protocols into EIGRP

Metric order: Bandwidth (Kbps), delay (tens of microseconds), reliability (255=100%), load (0-255, 255=100%loaded), MTU (1500)

Becareful in named mode EIGRP, metric 1 1 1 1 1 no longer works because you’re using wide metrics

router eigrp [AS] 
network 10.1.0.0 
redistribute static
redistribute ospf [metric] 
redistribute rip 
redistribute isis 
default-metric 10000 100 255 1 1500

OSPF

OSPF does not require a seed metric (cost), but one can be defined . The default value is 20, except for BGP which is 1. The subnet keyword needs to be defined on the redistributed protocol or only major nets will be redistributed.

There are 4 different route types for OSPF when redistributing,

E1>E2, N1>N2

Difference is how the cost is calculated

  • E1 – Normal area, type 5 LSA, external cost plus the internal cost to reach the route
  • E2 – Normal area, type 5 LSA, cost of route is always the external (20)
  • N1 – NSSA area, type 7 LSA, external cost plus the internal cost to reach the route
  • N2 – NSSA area, type 7 LSA, cost of route is always the external (20)
router ospf [process ID] 
network 10.10.0.0 0.0.255.255 area 0 
redistribute static metric 200 [subnets]
redistribute rip metric 200 [subnets] 
redistribute eigrp 1 metric 100 [subnets] 
redistribute isis metric 10 [subnets]

BGP

BGP does not use a seed metric when redistrbuting other protocols into it.

OSPF has specicial requirements when redistributing into BGP. Only intra-area and inter-area are included by default. You’ll need to use the external keyword if you want external OSPF routes to be included

router bgp [as]
redistribute static
redistribute eigrp [as]

redistribute isis ? 
 WORD ISO routing area tag
 clns Redistribution of OSI dynamic routes
 ip Redistribution of IP dynamic routes
 level-1 IS-IS level-1 routes only
 level-1-2 IS-IS level-1 and level-2 routes
 level-2 IS-IS level-2 routes only
 metric Metric for redistributed routes
 route-map Route map reference
 <cr>

redistribute ospf [pid] match 
redistribute ospf 1 match ?
 external Redistribute OSPF external routes
 internal Redistribute OSPF internal routes
 nssa-external Redistribute OSPF NSSA external routes


ISIS

Metrics for ISIS are between 1 – 63. There is no default metric and one should be configured. The default metric is 0 if one is not included.

router isis 
network 49.1234.1111.1111.1111.00
redistribute static
redistribute rip metric 20 
redistribute eigrp 1 metric 20 
redistribute ospf 1 metric 20

 

 

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