Transcript ROUTE10S04L03

Configuring and
Verifying Route
Redistribution
Implement an IPv4-Based Redistribution Solution
© 2009 Cisco Systems, Inc. All rights reserved.
ROUTE v1.0—4-1
Redistribution Supports All Protocols
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ROUTE v1.0—4-2
Steps to Configure Redistribution into
RIP
Enter router RIP configuration mode
R1(config-router)#
redistribute ospf 1
 Configure redistribution from another routing protocol; OSPF is
used above.
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.
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Redistributing into RIP
 Redistribute into RIP and assign the metric 3 (3 hops) to all
OSPF routes.
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Steps to Configure Redistribution into
OSPF
Enter router OSPF configuration mode
R1(config-router)#
redistribute eigrp 100 metric 100 subnets
 Configure redistribution from another routing protocol; EIGRP with
AS 10 is used above.
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>
 These optional parameters influence redistribution into OSPF
routing protocol.
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Redistributing into OSPF
 Redistribute from EIGRP AS 100 into OSPF and change the
metric type from type 2 to type 1.
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Steps to Configure Redistribution into
EIGRP
 Enter router EIGRP configuration mode
R1(config-router)#
redistribute ospf 1
 Configure redistribution from another routing protocol; OSPF with
process number 1 is used above.
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 EIGRP
routing protocol.
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Default Metric
R1(config-router)#
default-metric 10000 100 255 1 1500
 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
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Redistributing into EIGRP
 Redistribute OSPF 1 routing process updates into EIGRP AS 100
and overwrite the default metric.
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Example: Redistributing into OSPF Before Redistribution
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Example: Configuring Redistribution at
Router R2
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Example: Routing Tables After
Summarizing Routes and Redistributions
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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.
© 2009 Cisco Systems, Inc. All rights reserved.
Route Source
Default Distance
Connected interface
0
Static route
1
EIGRP summary route
5
External 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
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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
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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
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Modifying Administrative Distance
R1(config-router)#
distance ospf external 100 inter-area 100 intra-area 100
 Used for OSPF to define the external, interarea, and intra-area
distance
R1(config-router)#
distance eigrp 90 170
 Used for EIGRP to define the internal and external distance
R1(config-router)#
distance bgp 20 200 200
 Used for BGP to define external, internal, and local distance
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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.
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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.
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Example: Redistribution Using
Administrative Distance
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Example: Redistribution Using
Administrative Distance (Cont.)
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Example: Redistribution Using
Administrative Distance (Cont.)
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Example: Redistribution Using
Administrative Distance (Cont.)
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Example: Redistribution Using
Administrative Distance (Cont.)
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Redistribution to Prevent Routing Loops
 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
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Solution With Route Tagging
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Redistribution With Tagging Verification
 Routing table before tagging
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Redistribution With Tagging Verification
(Cont.)
 Routing table after tagging is applied to router R1
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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 the
trustworthiness 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.
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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.
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