Implement an IPv4-Based Redistribution Solution

© 2009 Cisco Systems, Inc. All rights reserved. ROUTE v1.0—4-1

Implement an IPv4-Based Redistribution Solution

Configuring and Verifying Route Redistribution


Redistribution Supports All Protocols


Steps to Configure Redistribution into RIPEnter router RIP configuration mode

Configure redistribution from another routing protocol; OSPF is used above.

redistribute ospf 1

R1(config-router)#

R1(config-router)# redistribute ospf 1 ? match Redistribution of OSPF routes metric Metric for redistributed routes route-map Route map reference … <cr>

These optional parameters influence redistribution into the RIP routing protocol.


Redistributing into RIP Redistribute into RIP and assign the metric 3 (3 hops) to all

OSPF routes.


Steps to Configure Redistribution into OSPFEnter router OSPF configuration mode

Configure redistribution from another routing protocol; EIGRP with AS 10 is used above.

These optional parameters influence redistribution into OSPF routing protocol.

redistribute eigrp 100 metric 100 subnets R1(config-router)#

R1(config-router)# redistribute eigrp 100 ? metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for

redistributed routes route-map Route map reference subnets Consider subnets for redistribution into OSPF tag Set tag for routes redistributed into OSPF … <cr>


Redistributing into OSPF Redistribute from EIGRP AS 100 into OSPF and change the

metric type from type 2 to type 1.


Steps to Configure Redistribution into EIGRP Enter router EIGRP configuration mode

Configure redistribution from another routing protocol; OSPF with process number 1 is used above.

These optional parameters influence redistribution into EIGRP routing protocol.

redistribute ospf 1R1(config-router)#

R1(config-router)#redistribute ospf 1 ? match Redistribution of OSPF routes metric Metric for redistributed routes route-map Route map reference …<cr>


Default Metric

The default metric is set to: Bandwidth in kilobits = 10000, Delay in tens of microseconds = 100, Reliability = 255 (maximum), Load = 1 (minimum), MTU = 1500 bytes

You need to use this command when redistributing from another protocol with incompatible metric into EIGRP.

You do not need this command when redistributing:– static routes to interface or connected networks– between EIGRP processes

R1(config-router)#

default-metric 10000 100 255 1 1500


Redistributing into EIGRP Redistribute OSPF 1 routing process updates into EIGRP AS 100

and overwrite the default metric.


Example: Redistributing into OSPF - Before Redistribution


Example: Configuring Redistribution at Router R2


Example: Routing Tables After Summarizing Routes and Redistributions


Route Source Default Distance

Connected interface 0

Static route 1

EIGRP summary route 5External BGP 20

Internal EIGRP 90

IGRP 100

OSPF 110

IS-IS 115

RIPv1, RIPv2 120

ODR 160

External EIGRP 170

Internal BGP 200

Unknown 255

Administrative Distance Administrative distance

(AD) is a way of ranking the trustworthiness of routing information.

A lower administrative distance means a route is more trustworthy.


Administrative Distance Example From R1 to R6:

– RIP (AD 120) will choose R1-R4-R6– OSPF (AD 110) will choose R1-R2-R3-R5-R6– EIGRP (AD 90) will choose R1-R2-R3-R5-R6


Steps to Configure Redistribution Using Administrative Distance Enter router configuration mode Configure the redistribution from another routing protocol Modify the administrative distance

– Remember that the configuration is different for different routing protocols


distance ospf external 100 inter-area 100 intra-area 100R1(config-router)#

Modifying Administrative Distance

Used for OSPF to define the external, interarea, and intra-area distance

Used for EIGRP to define the internal and external distance

Used for BGP to define external, internal, and local distance

distance eigrp 90 170R1(config-router)#

distance bgp 20 200 200R1(config-router)#


Modifying Administrative Distance (Cont.) The distance eigrp comand is used for EIGRP protocol. The distance (IP) command is protocol-independent

– Used to define an administrative distance for routes that are inserted into the routing table

– Used for all protocols, except for EIGRP, OSPF, and BGP when the dedicated, protocol-specific distance commands are used.


Modifying Administrative Distance (Cont.) The distance ospf comand is used for OSPF protocol. The distance (IP) command is protocol independent.

– Used to define an administrative distance for routes that are inserted into the routing table.

– Used for all protocols, except for EIGRP, OSPF ,and BGP when the dedicated, protocol-specific distance commands are used.


Example: Redistribution Using Administrative Distance


Example: Redistribution Using Administrative Distance (Cont.)








Simple redistribution results in a loop after a route is lost. To prevent routing loops use route maps with:

– Redistribution of internal routes only– Route tagging

Redistribution to Prevent Routing Loops


Solution With Route Tagging


Redistribution With Tagging Verification

Routing table before tagging


Redistribution With Tagging Verification (Cont.)

Routing table after tagging is applied to router R1


Summary Redistribution supports all routing protocols. Additionally, static

and connected routes can be redistributed to allow the routing protocol to advertise the routes without using a network statement for them.

Administrative distance (AD) is a way of ranking thetrustworthiness of routing information. A lower administrative distance indicates that a route is more trustworthy.

The distance (IP) command configures the administrative distance per specific network inserted into routing table, regardless of the IP routing protocol used. The specific protocol dependent distance commands are used to define administrative distance for a specific routing protocol.


Summary (Cont.) Redistribution using administrative distance can correct path

selection problems in a redistribution environment. It is very likely that routing loops are introduced when you use

multipoint two-way redistribution. Two solutions are to redistribute only internal routes and to use route tagging.

The show ip route command output for a specific network shows the tagging values added to a network during the redistribution process.


Implement an IPv4-Based Redistribution Solution

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