Shulou(Shulou.com)06/01 Report--

The eighth part of CCNP routing experiment: route rerelease

In the previous labs, you have learned about static and dynamic routing. Now, we need to learn how to make them converge in a network, that is, routing redistribution. Route redistribution can realize the sharing and exchange of routing information among multiple routing protocols, which makes it possible to support multiple routing protocols efficiently in the same internetwork. The router that performs route redistribution is called the border router. Because they are on the boundary of two or more autonomous systems.

When routing is redistributed, the unit of measurement and administrative distance are factors that must be considered. Each routing protocol has its own metrics, so metrics must be transformed to make them compatible during redistribution. The seed measure (Seed Metric) is defined in the route redistribution, which is the initial metric of a route redistributed from the outside. The default administrative distance for the routing protocol is as follows:

Route sourc

Administrative distance (AD)

Direct connection port

0

Use the exit as a static route

0

Use the next-hop address as the static route

one

EIGRP Summary rout

five

EBGP (external)

twenty

Internal EIGRP

ninety

IGRP

one hundred

OSPF

one hundred and ten

IS-IS autonomous system

one hundred and fifteen

RIP

one hundred and twenty

EGP external Gateway Protocol (obsolete)

one hundred and forty

ODR

one hundred and sixty

External EIGRP

170 (reissue)

IBGP (internal)

two hundred

Default rout

A default route is a way to deal with a router when it cannot find a specific route, and it is always used last

Unknown

two hundred and fifty five

Note:

Administrative distance refers to the routing credibility of a routing protocol. Under normal circumstances, the smaller the administrative distance, the higher the priority, that is, the higher the credibility! The router decides which protocol's route enters the routing table according to the administrative distance.

The static route AD configured with the outbound interface is actually between 0 and 1

If the AD is the same, the metric of the routing protocol (such as hop count or the broadband value of the link) is compared, and routes with lower metrics are placed in the routing table

The metric of distance vector routing protocols such as RIP and IGRP is hop count

The metric of OSPF is cost, and the default is 10 bandwidth / bandwidth (in bit/s)

If the AD and metrics are the same, then the routing protocol uses load balancing, that is, the packets sent are evenly distributed over each link.

All protocols can achieve load balancing. EIGRP and IGRP can support unequal cost load balancing of up to 4 links by default, and the value can reach 6 through the maximum-paths command.

Routes with an AD of 255will not be used

Route redistribution is not perfect, it has the following shortcomings:

Routing loops: depending on how redistribution is used, it is possible for a router to send routing information it receives from an AS back to this AS, which is similar to the split horizon problem of distance vector routing protocols.

Routing information is not compatible: different routing protocols use non-metric values, because these metrics may not be correctly introduced into different routing protocols, and the use of redistributed routing information for path selection may not be optimal.

Convergence time is different: different routing protocols have different convergence efficiency. for example, RIP converges more slowly than EIGRP, so if a link is DOWN down, EIGRP networks will learn this information earlier than RIP networks.

Do not overlap the use of routing protocols: do not use two different routing protocols in the same network, there should be clear boundaries between networks that use different routing protocols.

Redistribution principle: routes must be in the routing table before they can be redistributed

Use two-way redistribution in the case of a single boundary: two-way redistribution works steadily when there is only one border router in a network. If there is no mechanism to prevent routing loops, do not use two-way redistribution in a multi-boundary network. A combination of default routes, route filtering, and modifying administrative distance can prevent routing loops.

Use unidirectional redistribution when there are multiple border routers: if there is more than one router as the redistribution point, using unidirectional redistribution can avoid loopback and convergence problems. Use default routes on routers that do not need to receive external routes.

R1 configuration (Border Router)

R1#conf t

R1 (config) # int lo0

R1 (config-if) # desc Directly

R1 (config-if) # exit

R1 (config) # int f1and0

R1 (config-if) # desc static

R1 (config-if) # ip add 172.168.1.1 255.255.255.0

R1 (config-if) # no sh

R1 (config-if) # exit

R1 (config) # int s2and0

R1 (config-if) # desc Internet

R1 (config-if) # clock rate 64000

R1 (config-if) # ip add 202.100.100.1255.255.255.0

R1 (config-if) # no sh

R1 (config-if) # exit

R1 (config) # int e0Universe 0

R1 (config-if) # desc RIP

R1 (config-if) # no sh

R1 (config-if) # exit

R1 (config) # int e0bin1

R1 (config-if) # desc EIGRP

R1 (config-if) # no sh

R1 (config-if) # exit

R1 (config) # int e0bin2

R1 (config-if) # desc OSPF

R1 (config-if) # ip add 192.168.14.1255.255.255.0

R1 (config-if) # no sh

R1 (config-if) # exit

R1 (config-if) # desc IS-IS

R1 (config-if) # ip add 192.168.15.1255.255.255.0

R1 (config-if) # ip router isis / / declares the interface to the IS-IS routing process

R1 (config-if) # no sh

R1 (config-if) # exit

R1 (config) # ip route 0.0.0.0 0.0.0.0202.100.100.2 / / default route

R1 (config) # router rip / / enable RIP routing protocol

R1 (config-router) # version 2

R1 (config-router) # no auto-summary

R1 (config-router) # net 192.168.12.0

R1 (config-router) # exit

R1 (config) # router eigrp 1 / / enable the EIGRP routing protocol

R1 (config-router) # no auto-summary

R1 (config-router) # network 192.168.13.0255.255.255.0

R1 (config-router) # exit

R1 (config-router) # network 192.168.14.0255.255.255.0 area 0

R1 (config-router) # exit

R1 (config) # router isis / / enable IS-IS routing protocol

R1 (config-router) # net49.0001.1111.1111.1111.00

R1 (config-router) # exit

R2 configuration (RIP routing protocol)

R2#conf t

R2 (config) # int lo 0

R2 (config-if) # ip add 2.2.2.2 255.255.255.0

R2 (config-if) # desc RIP

R2 (config-if) # exit

R2 (config) # int e0Universe 0

R2 (config-if) # ip add 192.168.12.2255.255.255.0

R2 (config-if) # desc RIP

R2 (config-if) # exit

R2 (config) # int e0Universe 0

R2 (config-if) # no sh

R2 (config-if) # exit

R2 (config) # router rip

R2 (config-router) # ver 2

R2 (config-router) # no auto-summary

R2 (config-router) # net 2.2.2.0

R2 (config-router) # net 192.168.12.0

R2 (config-router) # exit

R3 configuration: (EIGRP routing protocol)

R3#conf t

R3 (config) # int lo0

R3 (config-if) # ip add 3.3.3.3255.255.255.0

R3 (config-if) # desc EIGRP

R3 (config-if) # exit

R3 (config) # int e0Let0

R3 (config-if) # desc EIGRP

R3 (config-if) # no sh

R3 (config-if) # exit

R3 (config) # router eigrp 1

R3 (config-router) # net 192.168.13.0

R3 (config-router) # net 3.3.3.0

R3 (config-router) # exit

R4 configuration: (OSPF routing protocol)

R4#conf t

R4 (config) # int lo0

R4 (config-if) # desc OSPF

R4 (config-if) # exit

R4 (config) # int e0Let0

R4 (config-if) # desc OSPF

R4 (config-if) # ip add 192.168.14.2255.255.255.0

R4 (config-if) # no sh

R4 (config-if) # exit

R4 (config) # router ospf 1

R4 (config-router) # net 4.4.4.0255.255.255.0 area 0

R4 (config-router) # exit

R5 configuration: (IS-IS routing protocol)

R5#conf t

R5 (config) # int lo0

R5 (config-if) # desc IS-IS

R5 (config-if) # ip add 5.5.5.5255.255.255.0

R5 (config-if) # ip router isis

R5 (config-if) # exit

R5 (config) # int e0Let0

R5 (config-if) # desc IS-IS

R5 (config-if) # ip add 192.168.15.2255.255.255.0

R5 (config-if) # ip router isis

R5 (config-if) # no sh

R5 (config-if) # exit

R5 (config) # router isis

R5 (config-router) # net49.0001.5555.5555.5555.00

R5 (config-router) # exit

Branch configuration (static routing)

Branch#conf t

Branch (config) # int lo0

Branch (config-if) # ip add 172.168.100.1255.255.255.0

Branch (config-if) # exit

Branch (config) # int fa0/0

Branch (config-if) # ip add 172.168.1.2255.255.255.0

Branch (config-if) # no sh

Branch (config-if) # exit

Branch (config) # ip route 0.0.0.0 0.0.0.0172.168.1.1 / / backhaul routing

Internet configuration:

Internet#conf t

Internet (config) # int lo0

Internet (config-if) # ip add 10.10.10.10255.255.255.0

Internet (config-if) # exit

Internet (config) # int s0Accorde 0

Internet (config-if) # clock rate 64000

Internet (config-if) # no sh

Internet (config-if) # exit

Internet (config) # ip route 0.0.0.0 0.0.0.0202.100.100.1 / / backhaul routing

After completing the above basic configuration, R1 runs a variety of routing protocols, which can interwork with all networks and is the boundary route on the network. At this time, using the route redistribution function on it, each routing protocol can exchange routing information. Let's start.

First, the static route, default route, directly connected route, EIGRP, OSPF, ISIS are injected into the RIP protocol of R2. When redistributing the route to the RIP area, the metric must be specified, otherwise it cannot be added to the routing table because the injected route metric will become infinite, so you must specify the metricvalue manually. Note that the metric of RIP cannot be greater than 15, because the maximum hop count of RIP is 16. You can set the default seed metric through "default-metric". Only redistributed static routes or default routes can not specify seed metrics.

R1#conf t

R1 (config) # router rip

R1 (config-router) # default-informationoriginate / / inject default route

R1 (config-router) # redistribute static// injects a static route

R1 (config-router) # redistribute connectedmetric 6 / / inject directly connected routes

R1 (config-router) # redistribute eigrp 1 metric 3ax / injected EIGRP routing

R1 (config-router) # redistribute ospf 1 metric 4 Plus / injected OSPF routing

R1 (config-router) # redistribute isis level-1-2 metric 5max / injected ISIS routing

R2#sh ip rou / / the routing table of R2 changes at this time. Notice the metricvalue of the routing code "R"

Codes: C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPF external type 1, E2-OSPF external type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidate default, U-per-user static route

O-ODR, P-periodic downloaded static route,

Gateway of last resort is 192.168.12.1to network 0.0.0.0

C 192.168.12.0/24 is directly connected, Ethernet0/0

1.0.0.0/24 is subnetted, 1 subnets

R 1.1.1.0 [120/6] via 192.168.12.1, 00:00:01, Ethernet0/0

R 192.168.13.0/24 [120/6] via 192.168.12.1, 00:00:01, Ethernet0/0

2.0.0.0/24 is subnetted, 1 subnets

C 2.2.2.0 is directly connected, Loopback0

R 192.168.14.0/24 [120/6] via 192.168.12.1, 00:00:01, Ethernet0/0

R 3.0.0.0/8 [120/3] via 192.168.12.1, 00:00:01, Ethernet0/0

R 192.168.15.0/24 [120/6] via 192.168.12.1, 00:00:02, Ethernet0/0

4.0.0.0/32 is subnetted, 1 subnets

R 4.4.4.4 [120/4] via 192.168.12.1, 00:00:02, Ethernet0/0

R 202.100.100.0/24 [120/6] via 192.168.12.1, 00:00:02, Ethernet0/0

5.0.0.0/24 is subnetted, 1 subnets

R 5.5.5.0 [120/5] via 192.168.12.1, 00:00:03, Ethernet0/0

172.168.0.0/24 is subnetted, 2 subnets

R 172.168.1.0 [120/6] via 192.168.12.1, 00:00:03, Ethernet0/0

R 172.168.100.0 [120/1] via 192.168.12.1, 00:00:03, Ethernet0/0

R* 0.0.0.0 via 0 [120max 1] 192.168.12.1, 00:00:03, Ethernet0/0

Second, static route, default route, directly connected route, RIP, OSPF, ISIS are injected into the EIGRP routing protocol of R3. Since the administrative distance of the route redistributed to EIGRP will become infinite, the parameter values of bandwidth, delay, reliability, load and MTU must be set manually. The seed measure specified with the parameter "metric" in the "Redistribute" command takes precedence over the default seed measure set by the "default-metric command" in route mode. Note that static, default, and directly connected values do not need to be specified.

R1#conf t

R1 (config) # router eigrp1

R1 (config-router) # redistribute static / / inject static and default routes, or use network0.0.0.0

R1 (config-router) # redistributeconnected// injects directly connected routes

R1 (config-router) # redistribute ripmetric 1000 255 1 1500 / / inject rip routing

R1 (config-router) # redistribute ospf 1metric 1000 255 1 1500 Candle / injected OSPF routing

R1 (config-router) # redistribute isislevel-1-2 metric 1000 100 255 1 1500 max / injected ISIS routing

R3#sh ip rou / / R3 routing table, redistributed route code is "D EX"

Codes: C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPF external type 1, E2-OSPF external type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidate default, U-per-user static route

O-ODR, P-periodic downloaded static route

Gateway of last resort is 192.168.13.1to network 0.0.0.0

D EX 192.168.12.0/24 [170/307200] via192.168.13.1, 00:00:04, Ethernet0/0

1.0.0.0/24 is subnetted, 1 subnets

D EX 1.1.1.0 [170/409600] via 192.168.13.1, 00:00:04, Ethernet0/0

C 192.168.13.0/24 is directly connected, Ethernet0/0

2.0.0.0/24 is subnetted, 1 subnets

D EX 2.2.2.0 [170/2611200] via 192.168.13.1, 00:11:03, Ethernet0/0

D EX 192.168.14.0/24 [170/307200] via192.168.13.1, 00:00:04, Ethernet0/0

3.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 3.3.3.0/24 is directly connected, Loopback0

D 3.0.0.0/8 is a summary, 01:24:53, Null0

D EX 192.168.15.0/24 [170/307200] via 192.168.13.1,00:00:05, Ethernet0/0

4.0.0.0/32 is subnetted, 1 subnets

D EX 4.4.4.4 [170/2611200] via 192.168.13.1, 00:09:40, Ethernet0/0

D EX 202.100.100.0/24 [170/2195456] via192.168.13.1, 00:00:20, Ethernet0/0

5.0.0.0/24 is subnetted, 1 subnets

D EX 5.5.5.0 [170/2611200] via 192.168.13.1, 00:09:15, Ethernet0/0

172.168.0.0/24 is subnetted, 2 subnets

D EX 172.168.1.0 [170/284160] via 192.168.13.1, 00:00:20, Ethernet0/0

D EX 172.168.100.0 [170/284160] via 192.168.13.1, 00:20:35, Ethernet0/0

D*EX 0.0.0.0/0 [170/2195456] via192.168.13.1, 00:20:35, Ethernet0/0

The third is to inject static route, default route, directly connected route, RIP, EIGRP, ISIS into the OSPF routing protocol of R4. The administrative distance is 110and the Metric is 20 at the time of rerelease. Of course, the external path cost can also be set through the "metric-type" setting type or the "metric" parameter. Note that subnets is required when republishing to ospf, otherwise only the main class network will be reissued.

R1#conf t

R1 (config) # router ospf 1

R1 (config-router) # default-informationoriginate / / inject default route

R1 (config-router) # redistribute connectedsubnets// injects directly connected routes

R1 (config-router) # redistribute staticsubnets// injects a static route

R1 (config-router) # redistribute ripsubnets// injects RIP routing

R1 (config-router) # redistribute eigrp 1subnets// injects EIGRP routing

R1 (config-router) # redistribute isislevel-1-2 subnets// injects ISIS routing

The route that R4#ship rou// redistributes into OSPF is learned by router R4 with the code "O E2"

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPF external type 1, E2-OSPF external type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidate default, U-per-user static route

O-ODR, P-periodic downloaded static route

Gateway of last resort is 192.168.14.1to network 0.0.0.0

O E2 192.168.12.0/24 [110/20] via192.168.14.1, 00:11:00, Ethernet0/0

1.0.0.0/24 is subnetted, 1 subnets

O E2 1.1.1.0 [110/20] via 192.168.14.1, 00:10:50, Ethernet0/0

O E2 192.168.13.0/24 [110/20] via192.168.14.1, 00:11:00, Ethernet0/0

2.0.0.0/24 is subnetted, 1 subnets

O E2 2.2.2.0 [110/20] via 192.168.14.1, 00:09:33, Ethernet0/0

C 192.168.14.0/24 is directly connected, Ethernet0/0

O E2 3.0.0.0/8 [110/20] via192.168.14.1, 00:08:47, Ethernet0/0

O E2 192.168.15.0/24 [110/20] via192.168.14.1, 00:11:01, Ethernet0/0

4.0.0.0/24 is subnetted, 1 subnets

C 4.4.4.0 is directly connected, Loopback0

O E2 202.100.100.0/24 [110/20] via192.168.14.1, 00:11:01, Ethernet0/0

5.0.0.0/24 is subnetted, 1 subnets

O E2 5.5.5.0 [110/20] via 192.168.14.1, 00:08:10, Ethernet0/0

172.168.0.0/24 is subnetted, 2 subnets

O E2 172.168.1.0 [110/20] via 192.168.14.1, 00:10:53, Ethernet0/0

O E2 172.168.100.0 [110/20] via 192.168.14.1, 00:10:18, Ethernet0/0

O*E2 0.0.0.0/0 [110/1] via 192.168.14.1,00:11:58, Ethernet0/0

The fourth injects static route, default route, directly connected route, RIP, EIGRP, ISIS into the ISIS routing protocol of R5, and the administrative distance is 115 and Metric is 10 at the time of rerelease. When redistributing other routing protocols to isis, the level-2 type must be used. The default is Level-2.

R1#conf t

R1 (config) # router isis

R1 (config-router) # default-informationoriginate / / inject default route

R1 (config-router) # redistribute static// injects a static route

R1 (config-router) # redistribute connected// injects directly connected routes

R1 (config-router) # redistribute rip// injects RIP routing

R1 (config-router) # redistribute ospf 1ramp / injected OSPF routing

R1 (config-router) # redistribute eigrp 1ramp / injected EIGRP routing

Routing table of R5#sh ip rou / / R5

Codes: C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPF external type 1, E2-OSPF external type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidate default, U-per-user static route

O-ODR, P-periodic downloaded static route

Gateway of last resort is 192.168.15.1to network 0.0.0.0

I L2 192.168.12.0/24 [115/10] via192.168.15.1, Ethernet0/0

1.0.0.0/24 is subnetted, 1 subnets

I L2 1.1.1.0 [115/10] via 192.168.15.1, Ethernet0/0

I L2 192.168.13.0/24 [115/10] via192.168.15.1, Ethernet0/0

2.0.0.0/24 is subnetted, 1 subnets

I L2 2.2.2.0 [115/10] via 192.168.15.1, Ethernet0/0

I L2 192.168.14.0/24 [115/10] via192.168.15.1, Ethernet0/0

I L2 3.0.0.0/8 [115/10] via192.168.15.1, Ethernet0/0

C 192.168.15.0/24 is directly connected, Ethernet0/0

4.0.0.0/32 is subnetted, 1 subnets

I L2 4.4.4.4 [115/10] via 192.168.15.1, Ethernet0/0

I L2 202.100.100.0/24 [115/10] via192.168.15.1, Ethernet0/0

5.0.0.0/24 is subnetted, 1 subnets

C 5.5.5.0 is directly connected, Loopback0

172.168.0.0/24 is subnetted, 2 subnets

I L2 172.168.1.0 [115/10] via 192.168.15.1, Ethernet0/0

I L2 172.168.100.0 [115/10] via 192.168.15.1,Ethernet0/0

I*L2 0.0.0.0/0 [115/10] via192.168.15.1, Ethernet0/0

Experiment 2. Reissue of multipoint and multidirectional routing

R2 configuration: (border routing)

R2#conft

R2 (config) # inte0/0

R2 (config-if) # ipadd 192.168.21.2 255.255.255.0

R2 (config-if) # nosh

R2 (config-if) # exit

R2 (config) # inte0/1

R2 (config-if) # ipadd 192.168.24.2 255.255.255.0

R2 (config-if) # nosh

R2 (config-if) # exit

R2 (config) # inte0/2

R2 (config-if) # ipadd 192.168.25.2 255.255.255.0

R2 (config-if) # nosh

R2 (config-if) # exit

R2 (config) # inte0/3

R2 (config-if) # ipadd 192.168.26.2 255.255.255.0

R2 (config-if) # iprouter isis

R2 (config-if) # nosh

R2 (config-if) # exit

R2 (config) # routerrip

R2 (config-router) # ver2

R2 (config-router) # noau

R2 (config-router) # net192.168.21.0

R2 (config-router) # exit

R2 (config) # routereigrp 1

R2 (config-router) # net192.168.24.0

R2 (config-router) # exit

R2 (config) # routerospf 1

R2 (config-router) # net192.168.25.0 255.255.255.0 area 0

R2 (config-router) # exit

R2 (config) # routerisis

R2 (config-router) # net49.0001.2222.2222.2222.00

R2 (config-router) # exit

R3 configuration (Border Router)

R3#conft

R3 (config) # inte0/0

R3 (config-if) # ipadd 192.168.31.3 255.255.255.0

R3 (config-if) # nosh

R3 (config-if) # exit

R3 (config) # inte0/1

R3 (config-if) # ipadd 192.168.34.3 255.255.255.0

R3 (config-if) # nosh

R3 (config-if) # exit

R3 (config) # inte0/2

R3 (config-if) # ipadd 192.168.35.3 255.255.255.0

R3 (config-if) # nosh

R3 (config-if) # exit

R3 (config) # inte0/3

R3 (config-if) # ipadd 192.168.36.3 255.255.255.0

R3 (config-if) # iprouter isis

R3 (config-if) # nosh

R3 (config-if) # exit

R3 (config) # routerrip

R3 (config-router) # ver2

R3 (config-router) # noau

R3 (config-router) # net192.168.31.0

R3 (config-router) # exit

R3 (config) # routereigrp 1

R3 (config-router) # net192.168.34.0

R3 (config-router) # exit

R3 (config) # routerospf 1

R3 (config-router) # net192.168.35.0 255.255.255.0 area 0

R3 (config-router) # exit

R3 (config) # routerisis

R3 (config-router) # net49.0001.3333.3333.3333.00

R3 (config-router) # exit

R1 configuration (rip routing protocol)

R1#conft

R1 (config) # inte0/0

R1 (config-if) # ipadd 192.168.21.1 255.255.255.0

R1 (config-if) # nosh

R1 (config-if) # exit

R1 (config) # inte0/1

R1 (config-if) # ipadd 192.168.31.1 255.255.255.0

R1 (config-if) # nosh

R1 (config-if) # exit

R1 (config-if) # ipadd 1.1.1.1 255.255.255.0

R1 (config-if) # exit

R1 (config) # routerrip

R1 (config-router) # ver2

R1 (config-router) # noau

R1 (config-router) # net192.168.21.0

R1 (config-router) # noau

R1 (config-router) # net192.168.31.0

R1 (config-router) # net1.1.1.0

R4 configuration (eigrp routing)

R4#conft

R4 (config) # inte0/0

R4 (config-if) # ipadd 192.168.24.4 255.255.255.0

R4 (config-if) # nosh

R4 (config-if) # exit

R4 (config) # inte0/1

R4 (config-if) # ipadd 192.168.34.4 255.255.255.0

R4 (config-if) # nosh

R4 (config-if) # exit

R4 (config) # routereigrp 1

R4 (config-router) # net192.168.34.0

R4 (config-router) # net192.168.24.0

First inject EIGRP, OSPF, ISIS into the RIP routing protocol of R1

R2#conft

R2 (config) # routerrip

R2 (config-router) # default-metric4

R2 (config-router) # redistributeeigrp 1

R2 (config-router) # redistributeospf 1

R2 (config-router) # redistributeisis level-1-2

R3#conft

R3 (config) # routerrip

R3 (config-router) # default-metric4

R3 (config-router) # redistributeeigrp 1

R3 (config-router) # redistributeospf 1

R3 (config-router) # redistributeisis level-1-2

The second injection of RIP, OSPF, ISIS into the EIGRP routing protocol of R4

R2#conft

R2 (config) # routereigrp 1

R2 (config-router) # default-metric1000 2500 255 1 1500

R2 (config-router) # redistributerip

R2 (config-router) # redistributeospf 1

R2 (config-router) # redistributeisis level-1-2

R3#conft

R3 (config) # routereigrp 1

R3 (config-router) # default-metric1000 2500 255 1 1500

R3 (config-router) # redistributerip

R3 (config-router) # redistributeospf 1

R3 (config-router) # redistributeisis level-1-2

The third injection of RIP, EIGRP, ISIS into the OSPF routing protocol of R5

R2#conft

R2 (config) # routerospf 1

R2 (config-router) # redistributerip subnets

R2 (config-router) # redistributeeigrp 1 subnets

R2 (config-router) # redistributeisis level-1-2 subnets

R3#conft

R3 (config) # routerospf 1

R3 (config-router) # redistributerip subnets

R3 (config-router) # redistributeeigrp 1 subnets

R3 (config-router) # redistributeisis level-1-2 subnets

The fourth injection of RIP, EIGRP, OSPF into the ISIS routing protocol of R6

R2#conf t

R2 (config) # routerisis

R2 (config-router) # redistributerip level-2

R2 (config-router) # redistributeeigrp 1 level-2

R2 (config-router) # redistributeospf 1 level-2

R3#conft

R3 (config-router) # redistributerip level-2

R3 (config-router) # redistributeeigrp 1 level-2

R3 (config-router) # redistributeospf 1 level-2

First look at the routing tables of R2 and R3 and notice that the route marked in red is not the best route, that is, there is a suboptimal route.

R2#ship rou

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPFexternal type 1, E2-OSPFexternal type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidatedefault, U-per-user static route

O-ODR, P-periodic downloaded static route

Gatewayof last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

I L2 1.1.1.0 [115/20] via192.168.26.6, Ethernet0/3

O E2 192.168.31.0/24 [110/20] via 192.168.25.5, 00:15:21,Ethernet0/2

C 192.168.25.0/24 is directly connected,Ethernet0/2

D 4.0.0.0/8 [90/409600] via 192.168.24.4,01:46:16, Ethernet0/1

C 192.168.24.0/24 is directly connected,Ethernet0/1

5.0.0.0/32 is subnetted, 1 subnets

O 5.5.5.5 [110/11] via 192.168.25.5,00:15:21, Ethernet0/2

6.0.0.0/24 is subnetted, 1 subnets

IL1 6.6.6.0 [115/20] via 192.168.26.6,Ethernet0/3

C 192.168.26.0/24 is directly connected,Ethernet0/3

C 192.168.21.0/24 is directly connected,Ethernet0/0

I L1192.168.36.0/24 [115/20] via 192.168.26.6, Ethernet0/3

D 192.168.34.0/24 [90/307200] via192.168.24.4, 01:46:19, Ethernet0/1

O 192.168.35.0/24 [110/20] via 192.168.25.5,00:15:25, Ethernet0/2

R3#ship rou

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPFexternal type 1, E2-OSPFexternal type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidatedefault, U-per-user static route

O-ODR, P-periodic downloaded staticroute

Gatewayof last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

O E2 1.1.1.0 [110/20] via192.168.35.5, 00:23:48, Ethernet0/2

C 192.168.31.0/24 is directly connected,Ethernet0/0

O 192.168.25.0/24 [110/20] via 192.168.35.5,00:23:48, Ethernet0/2

D 4.0.0.0/8 [90/409600] via 192.168.34.4,01:54:22, Ethernet0/1

D 192.168.24.0/24 [90/307200] via192.168.34.4, 01:54:22, Ethernet0/1

5.0.0.0/32 is subnetted, 1 subnets

O 5.5.5.5 [110/11] via 192.168.35.5,00:23:48, Ethernet0/2

6.0.0.0/24 is subnetted, 1 subnets

O E2 6.6.6.0 [110/20] via 192.168.35.5, 00:23:50, Ethernet0/2

I L1192.168.26.0/24 [115/20] via 192.168.36.6, Ethernet0/3

O E2 192.168.21.0/24 [110/20] via 192.168.35.5, 00:23:50,Ethernet0/2

C 192.168.36.0/24 is directly connected,Ethernet0/3

C 192.168.34.0/24 is directly connected,Ethernet0/1

C 192.168.35.0/24 is directly connected,Ethernet0/2

Analysis: this does not seem to be the case under a single point of redistribution because routes destined for one direction will not be redistributed. But the situation is different in the case of multi-point two-way, where the route you distribute will be redistributed by another protocol. If the routing protocol with high AD value is redistributed to the routing protocol with low AD value, there will be suboptimal routing, routing loop and other problems. On the contrary, this problem will not occur if the routing protocol with low AD value is redistributed to the routing protocol with high AD. Note that the error occurred on the border router. At this point, you need to use a routing policy to solve the problem, as follows

Route filtering does not allow loop-producing route entries into my router, so that there is no suboptimal path.

Modify the administrative distance AD to increase the AD value of the suboptimal route entry so that even if the router sees two route entries going to the same destination, it will not write the suboptimal route to the routing table. This method is better than the previous one in that if the best path is down, the suboptimal route becomes the backup route.

Here we modify the administrative distance, then look at the routing table of each router again, and notice the load balancing among R1, R4, R5, and R6.

R2#conf t

R2 (config) # routerrip

R2 (config-router) # distance111 / / modify the administrative distance of RIP external routes to be less than ISIS, ospf, Eigrp

R2 (config-router) # exit

R2 (config) # routerospf 1

R2 (config-router) # distanceospf external 170 / / the administrative distance of modified OSPF is greater than isis and rip, equal to eigrp

R3#conf t

R3 (config) # routerrip

R3 (config-router) # distance111

R3 (config-router) # exit

R3 (config) # routerospf 1

R3 (config-router) # distanceospf external 170

R2#ship rou

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPFexternal type 1, E2-OSPFexternal type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidatedefault, U-per-user static route

O-ODR, P-periodic downloaded static route

Gatewayof last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

R 1.1.1.0 [111/1] via 192.168.21.1,00:00:04, Ethernet0/0

R 192.168.31.0/24 [111/1] via 192.168.21.1,00:00:04, Ethernet0/0

C 192.168.25.0/24 is directly connected,Ethernet0/2

D 4.0.0.0/8 [90/409600] via 192.168.24.4,00:00:04, Ethernet0/1

C 192.168.24.0/24 is directly connected,Ethernet0/1

5.0.0.0/32 is subnetted, 1 subnets

O 5.5.5.5 [110/11] via 192.168.25.5,00:00:04, Ethernet0/2

6.0.0.0/24 is subnetted, 1 subnets

IL1 6.6.6.0 [115/20] via 192.168.26.6,Ethernet0/3

C 192.168.26.0/24 is directly connected,Ethernet0/3

C 192.168.21.0/24 is directly connected,Ethernet0/0

I L1192.168.36.0/24 [115/20] via 192.168.26.6, Ethernet0/3

D 192.168.34.0/24 [90/307200] via192.168.24.4, 00:00:08, Ethernet0/1

O 192.168.35.0/24 [110/20] via 192.168.25.5,00:00:08, Ethernet0/2

R3#ship rou

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPFexternal type 1, E2-OSPFexternal type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidatedefault, U-per-user static route

O-ODR, P-periodic downloaded staticroute

Gatewayof last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

R 1.1.1.0 [111/1] via 192.168.31.1,00:00:00, Ethernet0/0

C 192.168.31.0/24 is directly connected,Ethernet0/0

O 192.168.25.0/24 [110/20] via 192.168.35.5,00:00:01, Ethernet0/2

D 4.0.0.0/8 [90/409600] via 192.168.34.4,00:00:01, Ethernet0/1

D 192.168.24.0/24 [90/307200] via192.168.34.4, 00:00:01, Ethernet0/1

5.0.0.0/32 is subnetted, 1 subnets

O 5.5.5.5 [110/11] via 192.168.35.5,00:00:01, Ethernet0/2

6.0.0.0/24 is subnetted, 1 subnets

IL1 6.6.6.0 [115/20] via 192.168.36.6,Ethernet0/3

I L1192.168.26.0/24 [115/20] via 192.168.36.6, Ethernet0/3

R 192.168.21.0/24 [111/1] via 192.168.31.1,00:00:02, Ethernet0/0

C 192.168.36.0/24 is directly connected,Ethernet0/3

C 192.168.34.0/24 is directly connected,Ethernet0/1

C 192.168.35.0/24 is directly connected,Ethernet0/2

R1#ship rou

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPFexternal type 1, E2-OSPFexternal type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidatedefault, U-per-user static route

O-ODR, P-periodic downloaded staticroute

Gatewayof last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

C 1.1.1.0 is directly connected, Loopback0

C 192.168.31.0/24 is directly connected,Ethernet0/1

R 192.168.25.0/24 [120/4] via 192.168.31.3,00:00:20, Ethernet0/1

[120/4] via 192.168.21.2,00:00:14, Ethernet0/0

R 4.0.0.0/8 [120/4] via 192.168.31.3,00:00:20, Ethernet0/1

[120/4] via 192.168.21.2,00:00:14, Ethernet0/0

R 192.168.24.0/24 [120/4] via 192.168.31.3,00:00:20, Ethernet0/1

[120/4] via 192.168.21.2,00:00:14, Ethernet0/0

5.0.0.0/32 is subnetted, 1 subnets

R 5.5.5.5 [120/4] via 192.168.31.3,00:00:22, Ethernet0/1

[120/4] via 192.168.21.2,00:00:16, Ethernet0/0

6.0.0.0/24 is subnetted, 1 subnets

R 6.6.6.0 [120/4] via 192.168.31.3,00:00:24, Ethernet0/1

[120/4] via 192.168.21.2,00:00:17, Ethernet0/0

R 192.168.26.0/24 [120/4] via 192.168.31.3,00:00:24, Ethernet0/1

C 192.168.21.0/24 is directly connected,Ethernet0/0

R 192.168.36.0/24 [120/4] via 192.168.21.2,00:00:17, Ethernet0/0

R 192.168.34.0/24 [120/4] via 192.168.31.3,00:00:24, Ethernet0/1

[120/4] via 192.168.21.2,00:00:17, Ethernet0/0

R 192.168.35.0/24 [120/4] via 192.168.31.3,00:00:24, Ethernet0/1

[120/4] via 192.168.21.2,00:00:17, Ethernet0/0

R4#ship rou

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPFexternal type 1, E2-OSPFexternal type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidatedefault, U-per-user static route

O-ODR, P-periodic downloaded staticroute

Gatewayof last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

DEX 1.1.1.0 [170/3225600] via192.168.34.3, 00:00:07, Ethernet0/1

[170/3225600] via 192.168.24.2,00:00:07, Ethernet0/0

D EX192.168.31.0/24 [170/3225600] via 192.168.34.3, 00:00:07, Ethernet0/1

[170/3225600] via192.168.24.2, 00:00:07, Ethernet0/0

D EX192.168.25.0/24 [170/3225600] via 192.168.34.3, 00:00:07, Ethernet0/1

[170/3225600] via192.168.24.2, 00:00:07, Ethernet0/0

4.0.0.0/8 is variably subnetted, 2subnets, 2 masks

C 4.4.4.0/24 is directly connected, Loopback0

D 4.0.0.0/8 is a summary, 00:00:09, Null0

C 192.168.24.0/24 is directly connected,Ethernet0/0

5.0.0.0/32 is subnetted, 1 subnets

DEX 5.5.5.5 [170/3225600] via192.168.34.3, 00:00:09, Ethernet0/1

[170/3225600] via 192.168.24.2,00:00:09, Ethernet0/0

6.0.0.0/24 is subnetted, 1 subnets

DEX 6.6.6.0 [170/3225600] via192.168.34.3, 00:00:10, Ethernet0/1

[170/3225600] via 192.168.24.2,00:00:10, Ethernet0/0

D EX192.168.26.0/24 [170/3225600] via 192.168.34.3, 00:00:10, Ethernet0/1

D EX192.168.21.0/24 [170/3225600] via 192.168.34.3, 00:00:10, Ethernet0/1

[170/3225600] via192.168.24.2, 00:00:10, Ethernet0/0

D EX192.168.36.0/24 [170/3225600] via 192.168.24.2, 00:00:10, Ethernet0/0

C 192.168.34.0/24 is directly connected,Ethernet0/1

D EX192.168.35.0/24 [170/3225600] via 192.168.34.3, 00:00:10, Ethernet0/1

[170/3225600] via192.168.24.2, 00:00:10, Ethernet0/0

R5# ship rou

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPFexternal type 1, E2-OSPFexternal type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidatedefault, U-per-user static route

O-ODR, P-periodic downloaded staticroute

Gatewayof last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

OE2 1.1.1.0 [110/20] via 192.168.35.3,00:00:02, Ethernet0/1

[110/20] via 192.168.25.2,00:00:02, Ethernet0/0

O E2192.168.31.0/24 [110/20] via 192.168.35.3, 00:00:02, Ethernet0/1

[110/20] via 192.168.25.2,00:00:02, Ethernet0/0

C 192.168.25.0/24 is directly connected,Ethernet0/0

O E24.0.0.0/8 [110/20] via 192.168.35.3, 00:00:02, Ethernet0/1

[110/20] via 192.168.25.2,00:00:02, Ethernet0/0

O E2192.168.24.0/24 [110/20] via 192.168.35.3, 00:00:04, Ethernet0/1

[110/20] via 192.168.25.2,00:00:04, Ethernet0/0

5.0.0.0/24 is subnetted, 1 subnets

C 5.5.5.0 is directly connected, Loopback0

6.0.0.0/24 is subnetted, 1 subnets

OE2 6.6.6.0 [110/20] via 192.168.35.3,00:00:06, Ethernet0/1

[110/20] via 192.168.25.2,00:00:06, Ethernet0/0

O E2192.168.26.0/24 [110/20] via 192.168.35.3, 00:00:06, Ethernet0/1

O E2192.168.21.0/24 [110/20] via 192.168.35.3, 00:00:06, Ethernet0/1

[110/20] via 192.168.25.2,00:00:06, Ethernet0/0

O E2192.168.36.0/24 [110/20] via 192.168.25.2, 00:00:06, Ethernet0/0

O E2192.168.34.0/24 [110/20] via 192.168.35.3, 00:00:06, Ethernet0/1

[110/20] via 192.168.25.2,00:00:06, Ethernet0/0

C 192.168.35.0/24 is directly connected,Ethernet0/1

R6#ship rou

Codes:C-connected, S-static, R-RIP, M-mobile, B-BGP

D-EIGRP, EX-EIGRP external, O-OSPF, IA-OSPF inter area

N1-OSPF NSSA external type 1, N2-OSPF NSSA external type 2

E1-OSPFexternal type 1, E2-OSPFexternal type 2

I-IS-IS, su-IS-IS summary, L1-IS-IS level-1, L2-IS-IS level-2

Ia-IS-IS inter area, *-candidatedefault, U-per-user static route

O-ODR, P-periodic downloaded staticroute

Gatewayof last resort is not set

1.0.0.0/24 is subnetted, 1 subnets

IL2 1.1.1.0 [115/10] via 192.168.36.3,Ethernet0/1

[115/10] via 192.168.26.2,Ethernet0/0

I L2192.168.31.0/24 [115/10] via 192.168.36.3, Ethernet0/1

[115/10] via 192.168.26.2,Ethernet0/0

I L2192.168.25.0/24 [115/10] via 192.168.36.3, Ethernet0/1

[115/10] via 192.168.26.2,Ethernet0/0

I L24.0.0.0/8 [115/10] via 192.168.36.3, Ethernet0/1

[115/10] via 192.168.26.2,Ethernet0/0

I L2192.168.24.0/24 [115/10] via 192.168.36.3, Ethernet0/1

[115/10] via 192.168.26.2,Ethernet0/0

5.0.0.0/32 is subnetted, 1 subnets

IL2 5.5.5.5 [115/10] via 192.168.36.3,Ethernet0/1

[115/10] via 192.168.26.2,Ethernet0/0

6.0.0.0/24 is subnetted, 1 subnets

C 6.6.6.0 is directly connected, Loopback0

C 192.168.26.0/24 is directly connected,Ethernet0/0

I L2192.168.21.0/24 [115/10] via 192.168.36.3, Ethernet0/1

[115/10] via 192.168.26.2,Ethernet0/0

C 192.168.36.0/24 is directly connected,Ethernet0/1

I L2192.168.34.0/24 [115/10] via 192.168.36.3, Ethernet0/1

[115/10] via 192.168.26.2,Ethernet0/0

I L2192.168.35.0/24 [115/10] via 192.168.36.3, Ethernet0/1

[115/10] via 192.168.26.2,Eth

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