© 2000, Cisco Systems, Inc. 9-1 Optimizing Routing Update Operation Chapter 9

© 2000, Cisco Systems, Inc. BSCN v1.0—9-2 Objectives Upon completion of this chapter, you will be able to perform the following tasks: Select and configure the different ways to control route update traffic Configure route redistribution in a network that does not have redundant paths between dissimilar routing processes Configure route redistribution in a network that has redundant paths between dissimilar routing processes

© 2000, Cisco Systems, Inc. BSCN v1.0—9-3 Objectives (cont.) Resolve path selection problems that result in a redistributed network Verify route redistribution Configure policy-based routing using route maps Given a set of network requirements, configure redistribution between different routing domains and verify proper operation (within described guidelines) of your routers Given a set of network requirements, configure policy-based routing within your pod and verify proper operation (within described guidelines) of your routers

© 2000, Cisco Systems, Inc Redistribution Between Multiple Routing Protocols

© 2000, Cisco Systems, Inc. BSCN v1.0—9-5 Interim during conversion Application-specific protocols –One size does not always fit all Political boundaries –Groups that do not work and play nicely with others Mismatch between devices –Multivendor interoperability –Host-based routers When Do You Use Multiple Routing Protocols?

© 2000, Cisco Systems, Inc. BSCN v1.0—9-6 AS 200 IGRP S0S1 AS 300 EIGRP What Is Redistribution? A

© 2000, Cisco Systems, Inc. BSCN v1.0—9-7 Routes are learned from another routing protocol when a router redistributes the information between the protocols IP Routing Table I I I I IP Routing Table D EX D D D S1 Advertises Routes from EIGRP to IGRP S0 Advertises Routes from IGRP to EIGRP AS 200 IGRP S0S1 AS 300 EIGRP What Is Redistribution? A B C Boundary Router

© 2000, Cisco Systems, Inc. BSCN v1.0—9-8 Redistribution Implementation Considerations RIP EIGRP RIP AS 300 EIGRP RIP EIGR P Routing feedback –Suboptimal path selection –Routing loops Incompatible routing information Inconsistent convergence time

© 2000, Cisco Systems, Inc. BSCN v1.0—9-9 Different protocols use different metrics Metrics are difficult to compare algorithmically Therefore, need a selection process: 1—Which protocol do you believe the most? Use the administrative distance 2—Then decide which metric is the best Selecting the Best Route

© 2000, Cisco Systems, Inc. BSCN v1.0—9-10 Which Protocol to Believe? Connected interface 0 Static route out an interface0 Static route to a next hop1 EIGRP summary route5 External BGP20 Internal EIGRP90 IGRP100 OSPF110 IS-IS 115 RIP v1, v2120 EGP140 External EIGRP170 Internal BGP200 Unknown255 Route SourceDefault Distance

© 2000, Cisco Systems, Inc. BSCN v1.0—9-11 Seed Metric The first or seed metric for a route is derived from being directly connected to a router interface But redistributed routes are not physically connected –Use the default-metric command to establish the seed metric for the route –Once a compatible metric is established, the metric will increment just like any other route –Set default metric larger than the largest native metric

© 2000, Cisco Systems, Inc. BSCN v1.0—9-12 Redistribution Supports All Protocols RtrA(config-router)#redistribute ? bgp Border Gateway Protocol (BGP) connected Connected egp Exterior Gateway Protocol (EGP) eigrp Enhanced Interior Gateway Routing Protocol (EIGRP) igrp Interior Gateway Routing Protocol (IGRP) isis ISO IS-IS iso-igrp IGRP for OSI networks mobile Mobile routes odr On Demand stub Routes ospf Open Shortest Path First (OSPF) rip Routing Information Protocol (RIP) static Static routes

© 2000, Cisco Systems, Inc. BSCN v1.0—9-13 IPX RIP redistribution with EIGRP is enabled by default AppleTalk RTMP redistribution is enabled by default Redistribution of IGRP in the same autonomous system is automatic; manual if different autonomous system Other protocols require manual redistribution IPX EIGRP IPX AppleTalk IP AppleTalk IP Redistribution and EIGRP

© 2000, Cisco Systems, Inc Configuring Redistribution

© 2000, Cisco Systems, Inc. BSCN v1.0—9-15 Configuring Redistribution What do I need to determine before configuring redistribution? Identify the boundary routers where the protocols will run

© 2000, Cisco Systems, Inc. BSCN v1.0—9-16 Configuring Redistribution Identify the boundary routers where the protocols will run Determine which protocol is the core and which is the edge What do I need to determine before configuring redistribution?

© 2000, Cisco Systems, Inc. BSCN v1.0—9-17 Configuring Redistribution Identify the boundary routers where the protocols will run Determine which protocol is the core and which is the edge Determine the directions you want to redistribute the protocols What do I need to determine before configuring redistribution?

© 2000, Cisco Systems, Inc. BSCN v1.0—9-18 Configuring Redistribution into OSPF RtrA(config-router)#router ospf 1 RtrA(config-router)#redistribute eigrp ? Autonomous system number RtrA(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

© 2000, Cisco Systems, Inc. BSCN v1.0—9-19 Configuring Redistribution into EIGRP RtrA(config-router)#router eigrp 100 RtrA(config-router)#redistribute ospf ? Process ID RtrA(config-router)#redistribute ospf 1 ? match Redistribution of OSPF routes metric Metric for redistributed routes route-map Route map reference

© 2000, Cisco Systems, Inc. BSCN v1.0—9-20 Used for redistributing into OSPF, RIP, EGP, or BGP Configuring default-metric Router(config-router)#  default-metric bandwidth delay reliability loading mtu Router(config-router)#  default-metric number Used for redistributing into IGRP or EIGRP

© 2000, Cisco Systems, Inc. BSCN v1.0—9-21 Configuring Redistribution Edge Protocol Core Protocol Redistribute Default or Static Redistribute and Change Administrative Distance Redistribute and Filter

© 2000, Cisco Systems, Inc. BSCN v1.0—9-22 Router(config-router)# Prevents routing protocol updates from being generated on the interface passive-interface type number Using and Configuring passive-interface

© 2000, Cisco Systems, Inc. BSCN v1.0—9-23 Router(config)# ip route prefix mask address [distance ] [tag tag] [permanent] Router(config)# ip route prefix mask interface [distance ] [tag tag] [permanent] Using and Configuring Static Routes Defines a path using an interface Use if you do not have a route to the next-hop address Automatically redistributed in some cases Defines a path using a next-hop address Use if you have a route to the defined address Requires redistribution

© 2000, Cisco Systems, Inc. BSCN v1.0—9-24 router rip passive-interface Serial1 network ! ip route Serial1 p1r2#sh ip route Gateway of last resort is not set is subnetted, 2 subnets C is directly connected, Serial1 C is directly connected, Serial0 S is directly connected, Serial p2r2 p1r2 Static Route Example

© 2000, Cisco Systems, Inc. BSCN v1.0—9-25 Using and Configuring default-network / /24 p2r2 p1r / /24 p1r3#show ip route Gateway of last resort is to network /8 is variably subnetted, 7 subnets, 2 masks R /24 [120/1] via , 00:00:05, Ethernet0 C /24 is directly connected, Ethernet0 R /16 [120/1] via , 00:00:16, Ethernet0 R* /0 [120/1] via , 00:00:05, Ethernet0 p2r2: router rip network network ! ip classless ip default-network

© 2000, Cisco Systems, Inc. BSCN v1.0—9-26 Redistribution Example Using ip default-network P1R3 S0: /24 S1: /24 S1: /24 S0: /24 S0: /24 S1: /24 E0: /24 E0: /24 RIP S1: /24 S0: /24 S1: /24 OSPF S0: /24 S1: /24S0: /24 RIP P1R1 P1R2 P2R3 P2R1 P2R2

© 2000, Cisco Systems, Inc. BSCN v1.0—9-27 Redistribution Example Using ip default-network (cont.) P1R3-Boundary Router P1R1-Internal interface Serial0 ip address bandwidth 64 ! interface Serial1 ip address clockrate ! ! router rip network ! ip classless ! router ospf 200 redistribute rip metric 30 subnets network area 0 ! router rip network ! ip classless ip default-network ! Must Be On All RIP/IGRP Routers if Want to Use Default Route to Get to Unknown Subnets of Directly Connected Networks Must Be Enabled for Subnets. Must Be Enabled for Subnets.

© 2000, Cisco Systems, Inc. BSCN v1.0—9-28 Redistribution Example Using ip default-network (cont.) Boundary Router IP Routing Table P1R3#show ip route * /24 is subnetted, 6 subnets C is directly connected, Serial0 O E [110/30] via , 00:44:56, Ethernet0 C is directly connected, Serial1 R [120/1] via , 00:00:05, Serial0 [120/1] via , 00:00:17, Serial1 O E [110/30] via , 00:44:56, Ethernet0 O E [110/30] via , 00:44:56, Ethernet /24 is subnetted, 1 subnets C is directly connected, Ethernet0 RIP OSPF P1R3

© 2000, Cisco Systems, Inc. BSCN v1.0—9-29 Redistribution Example Using ip default-network (cont.) Internal Router IP Routing Table P1R1#show ip route /24 is subnetted, 3 subnets R [120/1] via , 00:00:24, Serial1 [120/1] via , 00:00:10, Serial0 C is directly connected, Serial0 C is directly connected, Serial1 R* /0 [120/1] via , 00:00:10, Serial0 P1R1 RIP Router forwards packets destined to /24 networks using the default route

© 2000, Cisco Systems, Inc Controlling Routing Update Traffic

© 2000, Cisco Systems, Inc. BSCN v1.0—9-31 Redistribution Implementation Guidelines IGRP/OSPF IGRP OSPF Redistribute Default or Static IGRP OSPF Redistribute Redistribute and Filter or Change Administrative Distance

© 2000, Cisco Systems, Inc. BSCN v1.0—9-32 Controlling Routing Update Traffic How can we prevent routing update traffic from crossing some of these links? Trans R200 Cen R300 R100 Rem Kb T-1 T-1 Frame Relay T-1 Frame Relay

© 2000, Cisco Systems, Inc. BSCN v1.0—9-33 Using Route Filters Routing update

© 2000, Cisco Systems, Inc. BSCN v1.0—9-34 Using Route Filters Determine interface Routing update

© 2000, Cisco Systems, Inc. BSCN v1.0—9-35 Using Route Filters Is there a filter for this interface? Determine interface Routing update

© 2000, Cisco Systems, Inc. BSCN v1.0—9-36 Using Route Filters Yes No Process packet normally End Is there an entry for this address? No Drop packet Is there a filter for this interface? Determine interface Routing update

© 2000, Cisco Systems, Inc. BSCN v1.0—9-37 Using Route Filters Process entry according to filter configuration End Yes No Process packet normally End Is there an entry for this address? No Drop packet Is there a filter for this interface? Determine interface Routing update

© 2000, Cisco Systems, Inc. BSCN v1.0—9-38 Use a standard access list to permit or deny routes Access list can be applied to transmitted (outbound) or received (inbound) routing updates Router(config-router)# distribute-list {access-list-number | name } out [interface-name | routing-process | autonomous-system number] Configuring Route Filtering Router(config-router)# distribute-list {access-list-number | name } in [type number] For Outbound Updates: For Inbound Updates:

© 2000, Cisco Systems, Inc. BSCN v1.0—9-39 Hides network using interface filtering IP Route Filtering Configuration Example S router eigrp 1 network network distribute-list 7 out s0 ! access-list 7 permit A B

© 2000, Cisco Systems, Inc. BSCN v1.0—9-40 D E IP Static Route Filtering Configuration Example ip route ip route ! router eigrp 1 network default-metric redistribute static distribute-list 3 out static ! access-list 3 permit passive-interface s S B passive-interface s S0 ABC D E

© 2000, Cisco Systems, Inc. BSCN v1.0—9-41 Used for all protocols except EIGRP and BGP redistribution Used for EIGRP redistribution Modifying Administrative Distance Router(config-router)#  distance weight [address mask [access-list-number | name ]] [ ip ] Router(config-router)#  distance eigrp internal-distance external-distance

© 2000, Cisco Systems, Inc. BSCN v1.0—9-42 Redistribution Example Using distance Trans R200 Cen Rem kbps T1 T1 Frame Relay S0.1 S0.2 T1 Frame Relay R300 R100

© 2000, Cisco Systems, Inc. BSCN v1.0—9-43 Redistribution Example Using distance (cont.) Administrative Distance Metric Cen#show ip route /24 is subnetted, 11 subnets I [100/158813] via , 00:00:02, TokenRing1 I [100/8976] via , 00:00:02, Serial0.1 I [100/8976] via , 00:00:02, Serial0.2 C is directly connected, Serial0.2 C is directly connected, Serial0.1 I [100/160250] via , 00:00:02, Serial0.1 I [100/8539] via , 00:00:02, TokenRing0 [100/8539] via , 00:00:03, TokenRing1 Cen IGRP With Only IGRP Running Everywhere:

© 2000, Cisco Systems, Inc. BSCN v1.0— Trans R200 Cen Rem kbps T1 T1 Frame Relay S0.1 S0.2 T1 Frame Relay R300 R100 IGRP RIP Redistribution Example Using distance (cont.)

© 2000, Cisco Systems, Inc. BSCN v1.0—9-45 Redistribution Example Using distance (cont.) Router CenRouter R200 router rip redistribute igrp 1 passive-interface Serial0.2 passive-interface TokenRing0 passive-interface TokenRing1 network default-metric 3 ! router igrp 1 redistribute rip passive-interface Serial0.1 network default-metric router rip redistribute igrp 1 passive-interface Serial0 passive-interface TokenRing0 network default-metric 3 ! router igrp 1 redistribute rip passive-interface Serial1 network default-metric

© 2000, Cisco Systems, Inc. BSCN v1.0—9-46 Router Cen has RIP and IGRP routes Cen#show ip route /24 is subnetted, 11 subnets R [120/2] via , 00:00:01, Serial0.1 R [120/1] via , 00:00:02, Serial0.1 I [100/8976] via , 00:00:02, Serial0.2 C is directly connected, Serial0.2 C is directly connected, Serial0.1 R [120/1] via , 00:00:02, Serial0.1 I [100/8539] via , 00:00:02, TokenRing0 [100/8539] via , 00:00:02, TokenRing1 IGRP With IGRP and RIP Running: RIP Cen Redistribution Example Using distance (cont.)

© 2000, Cisco Systems, Inc. BSCN v1.0—9-47 Redistribution Example Using distance (cont.) Trans R200 Cen Rem kbps T1 T1 Frame Relay S0.1 S0.2 T1 Frame Relay R300 R100 IGRP RIP

© 2000, Cisco Systems, Inc. BSCN v1.0—9-48 R200#show ip route Gateway of last resort is not set /24 is subnetted, 11 subnets I [100/ ] via , 00:00:37, TokenRing0 I [100/ ] via , 00:00:37, TokenRing0 I [100/9039] via , 00:00:37, TokenRing0 I [100/8539] via , 00:00:37, TokenRing0 I [100/8539] via , 00:00:37, TokenRing0 I [100/ ] via , 00:00:37, TokenRing0 C is directly connected, Serial0 Redistribution Example Using distance (cont.) Router R200 includes suboptimal paths R200 RIPIGRP With IGRP and RIP Running:

© 2000, Cisco Systems, Inc. BSCN v1.0—9-49 Redistribution Example Using distance (cont.) Router R200 router rip redistribute igrp 1 network default-metric 3 ! router igrp 1 redistribute rip network default-metric distance ! access-list 1 permit access-list 1 permit access-list 1 permit Router Cen router rip redistribute igrp 1 network default-metric 3 ! router igrp 1 redistribute rip network default-metric distance ! access-list 1 permit access-list 1 permit access-list 1 permit

© 2000, Cisco Systems, Inc. BSCN v1.0—9-50 Redistribution Example Using distance (cont.) Router R200 learns some RIP routes R200#show ip route /24 is subnetted, 11 subnets R [120/1] via , 00:00:19, Serial1 R [120/2] via , 00:00:19, Serial1 I [100/9039] via , 00:00:49, TokenRing0 I [100/8539] via , 00:00:49, TokenRing0 I [100/8539] via , 00:00:49, TokenRing0 R [120/1] via , 00:00:19, Serial1 C is directly connected, Serial0 R200 RIPIGRP With IGRP and RIP Running and Filtering:

© 2000, Cisco Systems, Inc Verifying Redistribution Operation

© 2000, Cisco Systems, Inc. BSCN v1.0—9-52 Displays the contents of the IP routing table Traces the path a packet takes show ip route Router# Verifying Redistribution Operation traceroute Router#

© 2000, Cisco Systems, Inc Written Exercise

© 2000, Cisco Systems, Inc Policy-Based Routing Using Route Maps

© 2000, Cisco Systems, Inc. BSCN v1.0—9-55 Route Maps Route maps are complex access lists: –Lines in access lists  statements in route maps –Access-list number  route-map name –Addresses and masks in access lists  match statements in route maps –Statements in route maps are numbered Can insert and delete statements in a route map Can edit match conditions in a statement –Route-map statement can modify matched route with set command

© 2000, Cisco Systems, Inc. BSCN v1.0—9-56 Route Map Configuration Router(config)# route-map map-tag [permit | deny] [sequence-number] Defines the conditions for policy routing Router(config-route-map)# match {conditions} Router(config-route-map)# set {actions} Defines the conditions to match Defines the action to be taken on a match

© 2000, Cisco Systems, Inc. BSCN v1.0—9-57 Route Map Explanation route-map demo permit 10 match x y z match a set b set c route-map demo permit 20 match q set r route-map demo permit 30

© 2000, Cisco Systems, Inc. BSCN v1.0—9-58 Policy-Based Routing Allows you to implement policies that selectively cause packets to take different paths Can also mark traffic with different TOS Since Cisco IOS Release 11.0

© 2000, Cisco Systems, Inc. BSCN v1.0—9-59 Policy-Based Routing Benefits Source-based transit provider selection –Different users go different ways Quality of service (QoS) –Set precedence or TOS, used with queuing Cost savings –Use high-cost links only when necessary Load sharing –Use multiple paths based on traffic characteristics

© 2000, Cisco Systems, Inc. BSCN v1.0—9-60 Policies Applied to incoming packets Implemented using route maps –Matching routes modified by set commands –If match criteria met and route map specified permit Control routing as specified by the set action –If match criteria met and route map specified deny –Normal (destination based) routing –If all sequences in the list checked and no matches Normal (destination based) routing

© 2000, Cisco Systems, Inc. BSCN v1.0—9-61 Policy Routing match Commands Router(config-route-map)# match ip address {access-list-number | name} [...access-list-number | name] Router(config-route-map)# match length min max Matches IP addresses for policy routing Matches Layer 3 length of packet for policy routing

© 2000, Cisco Systems, Inc. BSCN v1.0—9-62 Policy Routing set Commands Router(config-route-map)# set interface type number [...type number] Defines interface to which output packets Router(config-route-map)# set ip next-hop ip-address [...ip-address] Defines next hop to which output packets

© 2000, Cisco Systems, Inc. BSCN v1.0—9-63 Policy Routing set Commands(cont.) Router(config-route-map)# set default interface type number [...type number] Defines interface to output packets that have no explicit route to the destination Router(config-route-map)# set ip default next-hop ip-address [...ip-address] Defines next hop to output packets that have no explicit route to the destination

© 2000, Cisco Systems, Inc. BSCN v1.0—9-64 Configuring Policy-Based Routing Router(config-if)#  ip policy route-map map-tag Specify a route map to use for policy routing on an interface Router(config-if)#  ip route-cache policy Enable fast-switched policy routing

© 2000, Cisco Systems, Inc. BSCN v1.0—9-65 Policy-Based Routing Example S3: C A B S1: S0: S1: S2: S0: Router A has a policy that packets from go to Router C’s interface S1

© 2000, Cisco Systems, Inc. BSCN v1.0—9-66 Policy-Based Routing Example (cont.) RouterA(config)# interface Serial2 RouterA(config-if)# ip address RouterA(config-if)# ip policy route-map test RouterA(config)#route-map test permit 10 RouterA(config-route-map)#match ip address 1 RouterA(config-route-map)#set ip next-hop RouterA(config-route-map)#exit RouterA(config)#access-list 1 permit

© 2000, Cisco Systems, Inc Verifying Policy-Based Routing

© 2000, Cisco Systems, Inc. BSCN v1.0—9-68 Verifying Policy-Based Routing Router#  show ip policy Displays route maps configured on interfaces Router#  show route-map [map-name] Displays a route map

© 2000, Cisco Systems, Inc. BSCN v1.0—9-69 Verifying Policy-Based Routing (cont.) Router#  debug ip policy Enables display of IP policy routing events Router#  traceroute Extended traceroute allows specification of source address Router#  ping Extended ping allows specification of source address

© 2000, Cisco Systems, Inc. BSCN v1.0—9-70 Verifying Policy-Based Routing Examples RouterA#show ip policy Interface Route map Serial2 test RouterA#show route-map route-map test, permit, sequence 10 Match clauses: ip address (access-lists): 1 Set clauses: ip next-hop Policy routing matches: 3 packets, 168 bytes

© 2000, Cisco Systems, Inc. BSCN v1.0—9-71 Verifying Policy-Based Routing Examples (cont.) RouterA#debug ip policy Policy routing debugging is on RouterA#show logging... 11:50:51: IP: s= (Serial2), d= (Serial3), len 100, policy rejected -- normal forwarding... 11:51:25: IP: s= (Serial2), d= , len 100, policy match 11:51:25: IP: route map test, item 10, permit 11:51:25: IP: s= (Serial2), d= (Serial1), len 100, policyrouted 11:51:25: IP: Serial2 to Serial

© 2000, Cisco Systems, Inc Case Study

© 2000, Cisco Systems, Inc. BSCN v1.0—9-73 RIP Domain, Metric = Hops 1 Public Class C Supports Unix W/S, Servers RIP Domain, Metric = Hops 1 Public Class C Supports Unix W/S, Servers OSPF Domain, Metric = Cost 1 Public Class C Supports Acquisition Policy OSPF Domain, Metric = Cost 1 Public Class C Supports Acquisition Policy Private Address Space Network Private Address Space Network T-3 Case Study—Redistribution JKL’s Acquisition A A’s New Acquisition To JKL 3 Fast Ethernet Ethernet Serial DFHG IGRP Domain, Metric = Composite 1 Private Class A Supports Regional Campus Topology IGRP Domain, Metric = Composite 1 Private Class A Supports Regional Campus Topology BCAE

© 2000, Cisco Systems, Inc Lab Exercise

© 2000, Cisco Systems, Inc. BSCN v1.0—9-75 Summary After completing this chapter, you should be able to perform the following tasks: Select and configure the different ways to control route update traffic Configure route redistribution in a network that does not have redundant paths between dissimilar routing processes Configure route redistribution in a network that has redundant paths between dissimilar routing processes

© 2000, Cisco Systems, Inc. BSCN v1.0—9-76 Summary (cont.) Resolve path selection problems that result in a redistributed network Verify route redistribution Configure policy-based routing using route maps Given a set of network requirements, configure redistribution between different routing domains and verify proper operation (within described guidelines) of your routers Given a set of network requirements, configure policy-based routing within your pod and verify proper operation (within described guidelines) of your routers

© 2000, Cisco Systems, Inc. BSCN v1.0—9-77 Review Questions 1. What is redistribution? 2. What is the default administrative distance for IGRP? For RIP? For OSPF? 3. When configuring a default metric for redistributed routes, the metric should be set to a value ________ than the largest metric within the AS. 4. What command is used for policy-based routing to establish criteria based on the packet length?

© 2000, Cisco Systems, Inc. BSCN v1.0—9-78 Review Questions (cont.) 5. What command is used to configure filtering of the routing update traffic from an interface? What command mode is this command entered in? 6. What does the following command do? distance What are the benefits of policy-based routing? 8. Policy-based routing is applied to ________ packets?