Migrating from RIP to OSPF in the Core

Một phần của tài liệu CCNP practical studies routing (Trang 368 - 383)

In this scenario, you migrate a typical RIP network to OSPF in the core of the network and leave RIP on the edge of the network, where typically, on LAN-based segments, bandwidth is not a major concern.

IP addressing and loopback address assignments have already been completed.

Figure 8-3 displays the current RIP network that you migrate to OSPF.

Figure 8-3. RIP Topology

Loopbacks have been configured in R1, R2, and R3 to populate the IP routing tables.

The Class B network, 141.108.0.0, has been subnetted using a Class C mask

throughout. Because all RIP-enabled routers have a local interface configured using a Class C mask, network connectivity is maintained.

The current IP routing table on R1 is displayed in Example 8-21.

Example 8-21 show ip route on R1

R3#show ip route

141.108.0.0/24 is subnetted, 26 subnets

R 141.108.253.0 [120/1] via 141.108.255.2, 00:00:15, Serial1/0 [120/1] via 141.108.254.2, 00:00:11, Serial1/1 C 141.108.255.0 is directly connected, Serial1/0

C 141.108.254.0 is directly connected, Serial1/1 C 141.108.1.0 is directly connected, Ethernet0/0 C 141.108.3.0 is directly connected, Loopback1 C 141.108.2.0 is directly connected, Loopback0 C 141.108.5.0 is directly connected, Loopback3 C 141.108.4.0 is directly connected, Loopback2 C 141.108.7.0 is directly connected, Loopback5 C 141.108.6.0 is directly connected, Loopback4

R 141.108.9.0 [120/1] via 141.108.255.2, 00:00:16, Serial1/0 R 141.108.8.0 [120/1] via 141.108.255.2, 00:00:16, Serial1/0 R 141.108.11.0 [120/1] via 141.108.255.2, 00:00:16, Serial1/0 R 141.108.10.0 [120/1] via 141.108.255.2, 00:00:16, Serial1/0 R 141.108.13.0 [120/1] via 141.108.255.2, 00:00:16, Serial1/0 R 141.108.12.0 [120/1] via 141.108.255.2, 00:00:16, Serial1/0 R 141.108.15.0 [120/1] via 141.108.255.2, 00:00:17, Serial1/0 R 141.108.14.0 [120/1] via 141.108.255.2, 00:00:17, Serial1/0 R 141.108.17.0 [120/1] via 141.108.254.2, 00:00:12, Serial1/1 R 141.108.16.0 [120/1] via 141.108.254.2, 00:00:12, Serial1/1 R 141.108.19.0 [120/1] via 141.108.254.2, 00:00:12, Serial1/1 R 141.108.18.0 [120/1] via 141.108.254.2, 00:00:12, Serial1/1 R 141.108.21.0 [120/1] via 141.108.254.2, 00:00:12, Serial1/1 R 141.108.20.0 [120/1] via 141.108.254.2, 00:00:13, Serial1/1 R 141.108.23.0 [120/1] via 141.108.254.2, 00:00:13, Serial1/1 R 141.108.22.0 [120/1] via 141.108.254.2, 00:00:13, Serial1/1

Example 8-21 displays over 25 different networks. The main aim of converting the routing algorithm from RIP to OSPF is to enable VLSM in the WAN and summarization among routers to reduce IP routing table sizes.

Example 8-22 displays the current working configuration on R1 running RIP as the primary routing algorithm.

Example 8-22 R1's RIP Configuration

hostname R1

!

enable password cisco

!

ip subnet-zero

!

interface Loopback0

ip address 141.108.2.1 255.255.255.0

!

interface Loopback1

ip address 141.108.3.1 255.255.255.0

!

interface Loopback2

ip address 141.108.4.1 255.255.255.0

!

interface Loopback3

ip address 141.108.5.1 255.255.255.0

!

interface Loopback4

ip address 141.108.6.1 255.255.255.0

!

interface Loopback5

ip address 141.108.7.1 255.255.255.0

!

interface Ethernet0/0

ip address 141.108.1.1 255.255.255.0 interface Serial1/0

ip address 141.108.255.1 255.255.255.0 clockrate 128000

!

interface Serial1/1

ip address 141.108.254.1 255.255.255.0 clockrate 128000

!

router rip

network 141.108.0.0

!

line con 0 end

Example 8-23 displays R2's current working configuration.

Example 8-23 R2's RIP Configuration

hostname R2

!

enable password cisco interface Loopback0

ip address 141.108.9.1 255.255.255.0

!

interface Loopback1

ip address 141.108.10.1 255.255.255.0

!

interface Loopback2

ip address 141.108.11.1 255.255.255.0

!

interface Loopback3

ip address 141.108.12.1 255.255.255.0

!

interface Loopback4

ip address 141.108.13.1 255.255.255.0

!

interface Loopback5

ip address 141.108.14.1 255.255.255.0

!

interface Loopback6

ip address 141.108.15.1 255.255.255.0

!

interface Ethernet0/0

ip address 141.108.8.1 255.255.255.0

!

interface Serial1/0 bandwidth 128

ip address 141.108.255.2 255.255.255.0

!

interface Serial1/1

ip address 141.108.253.2 255.255.255.0 router rip

network 141.108.0.0

!

ip classless

! end

Example 8-24 displays R3's current working configuration.

Example 8-24 R3's RIP Configuration

hostname R3

!

enable password cisco

!

no ip domain-lookup

!

interface Loopback0

ip address 141.108.17.1 255.255.255.0

!

interface Loopback1

ip address 141.108.18.1 255.255.255.0

!

interface Loopback2

ip address 141.108.19.1 255.255.255.0

!

interface Loopback3

ip address 141.108.20.1 255.255.255.0

!

interface Loopback4

ip address 141.108.21.1 255.255.255.0

!

interface Loopback5

ip address 141.108.22.1 255.255.255.0

!

interface Loopback6

ip address 141.108.23.1 255.255.255.0

!

interface Ethernet0

ip address 141.108.16.1 255.255.255.0

!

interface Serial0

ip address 141.108.254.2 255.255.255.0 bandwidth 125

!

interface Serial1

ip address 141.108.253.1 255.255.255.0 bandwidth 125

clockrate 125000

!

router rip

network 141.108.0.0

! end

To start, add OSPF to the center of the network, and place all the WAN interfaces in area 0. Maintain the Class C mask for now to make redistribution relativity easy to configure. This step is common when migrating from one protocol to another.

Example 8-25 configures R1 for OSPF across the WAN to R1 and R2. You take the same configuration steps on R2 and R3.

Example 8-25 OSPF Configuration on R1

R1(config)#router ospf1

R1(config-router)#network 141.108.255.0 0.0.0.255 area 0 R1(config-router)#network 141.108.254.0 0.0.0.255 area 0 R1(config-router)#router rip

R1(config-router)#passive-interface serial 1/0 R1(config-router)#passive-interface serial 1/1

R1 is configured not to send any RIP updates to Serial 1/0 (to R2) and Serial 1/1 (to R3); this configuration stops the sending of unnecessary updates across WAN links.

At this stage, you have not configured any redistribution, so there is no connectivity among the Ethernet and loopback interfaces. Example 8-26 confirms the status of IP connectivity after the show ip route command is entered on R1.

Example 8-26 show ip route on R1

R1#show ip route

141.108.0.0/24 is subnetted, 10 subnets

O 141.108.253.0 [110/1562] via 141.108.255.2, 00:00:04, Serial1/0 C 141.108.255.0 is directly connected, Serial1/0

C 141.108.254.0 is directly connected, Serial1/1 C 141.108.1.0 is directly connected, Ethernet0/0 C 141.108.3.0 is directly connected, Loopback1 C 141.108.2.0 is directly connected, Loopback0 C 141.108.5.0 is directly connected, Loopback3 C 141.108.4.0 is directly connected, Loopback2 C 141.108.7.0 is directly connected, Loopback5 C 141.108.6.0 is directly connected, Loopback4

The only visible route on R1 is the locally connected routes and the WAN circuit between R2 and R3.

Next, configure redistribution on routers R1, R2, and R3 to advertise the RIP networks to the OSPF backbone.

Example 8-27 displays the RIP to OSPF redistribution on R1. Example 8-27 also displays redistribution from OSPF to RIP to allow communication from R2/R3

Ethernet segments to R1's locally connected network, which, at the moment, is advertised by only RIP. The ? tool is used to display the available options.

Example 8-27 Redistribution on R1

R1(config)#router ospf 1

R1(config-router)#redistribute rip metric ? <0-16777214> OSPF default metric

R1(config-router)#redistribute rip metric 100 subnets R1(config-router)#exit

R1(config)#router rip

R1(config-router)#redistribute ospf 1 metric ? <0-4294967295> Default metric

R1(config-router)#redistribute ospf 1 metric 3 R1(config-router)#distribute-list 1 out

R1(config-router)#exit

R1(config)#access-list 1 deny 141.108.1.0 0.0.0.255 R1(config)#access-list 1 deny 141.108.2.0 0.0.0.255 R1(config)#access-list 1 deny 141.108.3.0 0.0.0.255 R1(config)#access-list 1 deny 141.108.4.0 0.0.0.255 R1(config)#access-list 1 deny 141.108.5.0 0.0.0.255 R1(config)#access-list 1 deny 141.108.6.0 0.0.0.255 R1(config)#access-list 1 deny 141.108.7.0 0.0.0.255 R1(config)#access-list 1 permit any

R1 is now configured to redistribute from RIP to OSPF and vice versa. Example 8-27 displays the keyword subnets because the Class B network 141.108.0.0 has been subnetted across the network. Without this keyword, only classful networks would not be advertised. (In this case, you are using classless networks on all routers.) Also, the metrics have been set to 100 for all RIP-to-OSPF networks, and the hop count for all redistributed OSPF networks into RIP is set to 3.

Typically, networks have some other paths or back doors between any given routing topologies. To ensure that networks residing on R1 are never advertised by the OSPF backbone, the distribution list on R1 denies any networks residing in 141.108.1.0–

141.108.7.255 from being advertised from OSPF to RIP. This ensures that a routing loop cannot occur.

The access list 1, previously defined with seven statements, can be replaced with the configuration in Example 8-28 to deny the range of networks 141.108.0.0–

141.108.7.0 and permit all other networks.

Example 8-28 replaces the seven-line access list with two lines of IOS configuration.

(The no access-list 1 command removes the configuration currently present for access list 1.)

Example 8-28 Access List Configuration on R1

R1(config)#no access-list 1

R1(config)#access-list 1 deny 141.108.0.0 0.0.7.255 R1(config)#access-list 1 permit any

Example 8-29 displays the redistribution and filtering required on R2.

Example 8-29 Redistribution on R2

R2(config)#router rip

R2(config-router)#distribute-list 1 out

R2(config-router)#redistribute ospf 1 metric 3 R2(config-router)#router ospf 1

R2(config-router)#redistribute rip metric 10 subnets R2(config)#access-list 1 deny 141.108.8.0 0.0.7.255 R2(config)#access-list 1 permit any

Example 8-30 displays the redistribution and filtering on R3.

Example 8-30 Redistribution on R3

R3(config)#router rip

R3(config-router)#redistribute ospf 1 metric 3 R3(config-router)#distribute-list 1 out

R3(config-router)#router ospf 1

R3(config-router)#redistribute rip metric 10 subnets R3(config-router)#exit

R3(config)#access-list 1 deny 141.108.23.0 0.0.7.255 R3(config)#access-list 1 permit any

Confirm IP routing connectivity from R1. Example 8-31 displays the IP routing table on R1 and some sample ping requests that conform IP connectivity.

Example 8-31 show ip route and Pings on R1

R1#show ip route

Codes: C - connected,E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

141.108.0.0/24 is subnetted, 26 subnets

O 141.108.253.0 [110/1562] via 141.108.255.2, 00:00:51, Serial1/0 C 141.108.255.0 is directly connected, Serial1/0

C 141.108.254.0 is directly connected, Serial1/1 C 141.108.1.0 is directly connected, Ethernet0/0 C 141.108.3.0 is directly connected, Loopback1 C 141.108.2.0 is directly connected, Loopback0 C 141.108.5.0 is directly connected, Loopback3 C 141.108.4.0 is directly connected, Loopback2 C 141.108.7.0 is directly connected, Loopback5 C 141.108.6.0 is directly connected, Loopback4

O E2 141.108.9.0 [110/10] via 141.108.255.2, 00:00:51, Serial1/0 O E2 141.108.8.0 [110/10] via 141.108.255.2, 00:00:51, Serial1/0 O E2 141.108.11.0 [110/10] via 141.108.255.2, 00:00:51, Serial1/0 O E2 141.108.10.0 [110/10] via 141.108.255.2, 00:00:51, Serial1/0 O E2 141.108.13.0 [110/10] via 141.108.255.2, 00:00:51, Serial1/0 O E2 141.108.12.0 [110/10] via 141.108.255.2, 00:00:51, Serial1/0 O E2 141.108.15.0 [110/10] via 141.108.255.2, 00:00:51, Serial1/0 O E2 141.108.14.0 [110/10] via 141.108.255.2, 00:00:52, Serial1/0 O E2 141.108.17.0 [110/10] via 141.108.254.2, 00:00:52, Serial1/1 O E2 141.108.16.0 [110/10] via 141.108.254.2, 00:00:52, Serial1/1 O E2 141.108.19.0 [110/10] via 141.108.254.2, 00:00:52, Serial1/1 O E2 141.108.18.0 [110/10] via 141.108.254.2, 00:00:52, Serial1/1 O E2 141.108.21.0 [110/10] via 141.108.254.2, 00:00:52, Serial1/1 O E2 141.108.20.0 [110/10] via 141.108.254.2, 00:00:52, Serial1/1 O E2 141.108.23.0 [110/10] via 141.108.254.2, 00:00:52, Serial1/1

O E2 141.108.22.0 [110/10] via 141.108.254.2, 00:00:52, Serial1/1 R1#ping 141.108.9.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 141.108.9.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/16/16 ms R1#ping 141.108.22.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 141.108.22.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 12/14/16 ms The next step in migration is to remove RIP and enable OSPF across all interfaces in the networks. Before you complete this migration, look at the routing configurations on Routers R1, R2, and R3.

Example 8-32 displays the IP routing configuration on R1.

Example 8-32 show running-config (Truncated) on R1

router ospf 1

redistribute rip metric 100 subnets network 141.108.254.0 0.0.0.255 area 0 network 141.108.255.0 0.0.0.255 area 0

!

router rip

redistribute ospf 1 metric 3 passive-interface Serial1/0 passive-interface Serial1/1 network 141.108.0.0

distribute-list 1 out

access-list 1 deny 141.108.0.0 0.0.7.255 access-list 1 permit any

Example 8-33 displays the IP routing configuration on R2.

Example 8-33 show running-config (Truncated) on R2

router ospf 1

redistribute rip metric 10 subnets network 141.108.253.0 0.0.0.255 area 0 network 141.108.255.0 0.0.0.255 area 0

!

router rip

redistribute ospf 1 metric 3 passive-interface Serial1/0 passive-interface Serial1/1 network 141.108.0.0

distribute-list 1 out

!

ip classless

!

access-list 1 deny 141.108.8.0 0.0.7.255 access-list 1 permit any

Example 8-34 displays the IP routing configuration on R3.

Example 8-34 show running-config (Truncated) on R3

router ospf 1

redistribute rip metric 10 subnets network 141.108.254.0 0.0.0.255 area 0 network 141.108.253.0 0.0.0.255 area 0

!

router rip

redistribute ospf 1 metric 3 passive-interface Serial0 passive-interface Serial1 network 141.108.0.0

distribute-list 1 out

!

access-list 1 deny 141.108.16.0 0.0.7.255 access-list 1 permit any

Figure 8-4 displays the OSPF area assignment to complete the RIP to OSPF migration.

Figure 8-4. OSPF Area Assignments

Figure 8-4 displays the OSPF area assignment along with the ability to re-address the WAN circuit to /30 subnets because OSPF understands VLSM.

Example 8-35 displays the removal of RIP on R1 and the OSPF and IP address assignment on R1. Also, note the new IP address assignment for the WAN links with /30 subnets.

Example 8-35 Removal of RIP on R1 and OSPF/IP Address Assignment

R1(config)#no router rip R1(config)#router ospf 1

R1(config-router)#network 141.108.255.0 0.0.0.255 area 0 R1(config-router)#network 141.108.0.0 0.0.7.255 area 1 R1(config)#interface s1/0

R1(config-if)#ip address 141.108.255.1 255.255.255.252 R1(config-if)#interface s1/1

R1(config-if)#ip address 141.108.255.5 255.255.255.252

Example 8-36 displays the removal of RIP on R2 and the OSPF and IP address assignment on R2.

Example 8-36 Removal of RIP on R2 and OSPF/IP Address Assignment

R2(config)#no router rip R2(config)#router ospf 1

R2(config-router)#network 141.108.255.0 0.0.0.255 area 0 R2(config-router)#network 141.108.8.0 0.0.7.255 area 2 R2(config-router)#exit

R2(config)#interface s1/0

R2(config-if)#ip address 141.108.255.2 255.255.255.252 R2(config-if)#interface s1/1

R2(config-if)#ip address 141.108.255.10 255.255.255.252

Example 8-37 displays the removal of RIP on R3 and the OSPF and IP address assignment on R3.

Example 8-37 Removal of RIP on R3 and OSPF/IP Address Assignment

R3(config)#router ospf 1

R3(config-router)#network 141.108.23.0 0.0.7.255 area 3 R3(config-router)#network 141.108.255.0 0.0.0.255 area 0 R3(config-router)#exit

R3(config)#interface serial0

R3(config-if)#ip address 141.108.255.6 255.255.255.252 R3(config-if)#interface serial1

R3(config-if)#ip address 141.108.255.9 255.255.255.252

NOTE

Removing RIP from Routers R1, R2, and R3 causes the Cisco IOS to remove any redistribution between RIP and OSPF automatically. Therefore, manual removal of redistribution is not required on Routers R1, R2, and R3.

Now that OSPF is configured across all routers, view the IP routing table on R1.

Example 8-38 displays R1's IP routing table.

Example 8-38 R1's IP Routing Table

R1#show ip route

Codes: C - connected, , O - OSPF, IA - OSPF inter area

141.108.0.0/16 is variably subnetted, 26 subnets, 3 masks O 141.108.255.8/30 [110/1562] via 141.108.255.2, 00:00:27, Serial1/0

C 141.108.255.4/30 is directly connected, Serial1/1 C 141.108.255.0/30 is directly connected, Serial1/0 C 141.108.1.0/24 is directly connected, Ethernet0/0 C 141.108.3.0/24 is directly connected, Loopback1 C 141.108.2.0/24 is directly connected, Loopback0 C 141.108.5.0/24 is directly connected, Loopback3 C 141.108.4.0/24 is directly connected, Loopback2 C 141.108.7.0/24 is directly connected, Loopback5 C 141.108.6.0/24 is directly connected, Loopback4

O IA 141.108.9.1/32 [110/782] via 141.108.255.2, 00:00:27, Serial1/0 O IA 141.108.8.0/24 [110/791] via 141.108.255.2, 00:00:27, Serial1/0 O IA 141.108.10.1/32 [110/782] via 141.108.255.2, 00:00:27,

Serial1/0

O IA 141.108.11.1/32 [110/782] via 141.108.255.2, 00:00:27, Serial1/0

O IA 141.108.12.1/32 [110/782] via 141.108.255.2, 00:00:27, Serial1/0

O IA 141.108.13.1/32 [110/782] via 141.108.255.2, 00:00:28, Serial1/0

O IA 141.108.14.1/32 [110/782] via 141.108.255.2, 00:00:28, Serial1/0

O IA 141.108.15.1/32 [110/782] via 141.108.255.2, 00:00:28, Serial1/0

O IA 141.108.17.1/32 [110/782] via 141.108.255.6, 00:00:28, Serial1/1

O IA 141.108.16.0/24 [110/791] via 141.108.255.6, 00:00:28, Serial1/1

O IA 141.108.18.1/32 [110/782] via 141.108.255.6, 00:00:28, Serial1/1

O IA 141.108.19.1/32 [110/782] via 141.108.255.6, 00:00:28, Serial1/1

O IA 141.108.20.1/32 [110/782] via 141.108.255.6, 00:00:28, Serial1/1

O IA 141.108.21.1/32 [110/782] via 141.108.255.6, 00:00:28, Serial1/1

O IA 141.108.22.1/32 [110/782] via 141.108.255.6, 00:00:28, Serial1/1

O IA 141.108.23.1/32 [110/782] via 141.108.255.6, 00:00:28, Serial1/1

In Example 8-32, the redistributed routes appear as E2 (External Type 2) and OSPF is configured across all three routers. The OSPF type route is displayed as O IA in Example 8-38.

OSPF can support VLSM and network summarization, so configure each router in Figure 8-4 to summarize locally connected routes, which are contiguous. (All routers

are ABRs because each router resides in areas 0, 1, 2, or 3.) Example 8-39 displays the summarization for networks 141.108.0.0–141.108.7.0. To summarize internal OSPF routes, the area area-id range network subnet mask IOS command is required.

The loopback addresses on R1 reside in OSPF area 1. Example 8-39 displays the area summary command on R1.

Example 8-39 Area Summary on R1

R1(config)#router ospf 1 R1(config-router)#area 1 ?

authentication Enable authentication

default-cost Set the summary default-cost of a NSSA/stub area nssa Specify a NSSA area

range Summarize routes matching address/mask (border routers only)

stub Specify a stub area

virtual-link Define a virtual link and its parameters R1(config-router)#area 1 range ?

A.B.C.D IP address to match

R1(config-router)#area 1 range 141.108.0.0 ? A.B.C.D IP mask for address

R1(config-router)#area 1 range 141.108.0.0 255.255.248.0

The ? tool is used to display the various options. The mask, 255.255.248.0,

encompasses the seven networks ranging from 141.108.0.0–141.108.7.0. You may ask yourself why you are not using 141.108.0.0 on R1 or subnet zero. With large IP networks, the network IP designer should always use all the address space available;

subnet zero is a perfect example.

To enable subnet zero, you must configure the global ip subnet-zero command on R1.

Example 8-40 enables the use of zero subnets on R1.

Example 8-40 Subnet Zero Enabling on R1

R1(config)#ip subnet-zero

R1(config-if)#interface loopback 6

R1(config-if)#ip address 141.108.0.1 255.255.255.0

Example 8-41 displays the summarization required on R2 to encompass the networks 141.108.8.0–141.108.15.255. (These networks reside in area 2.)

Example 8-41 Area Summary on R2

R2(config)#router ospf 1

R2(config-router)#area 2 range 141.108.8.0 255.255.248.0

Example 8-42 displays the summarization required on R3 to encompass the networks 141.108.16.0–141.108.23.255. (These networks reside in area 3.)

Example 8-42 Area Summary on R2

R3(config)#router ospf 1

R3(config-router)#area 3 range 141.108.16.0 255.255.248.0

Example 8-43 displays the OSPF IP routing table on R1. (Initially, when RIP was the primary routing algorithm, you had 17 RIP entries, as displayed in Example 8-21.)

Example 8-43 show ip route ospf on R1

R1#show ip route ospf

141.108.0.0/16 is variably subnetted, 13 subnets, 3 masks O 141.108.255.8/30 [110/1562] via 141.108.255.2, 00:04:57, Serial1/0

O IA 141.108.8.0/21 [110/791] via 141.108.255.2, 00:04:57, Serial1/0 O IA 141.108.16.0/21 [110/782] via 141.108.255.6, 00:01:13,

Serial1/1

R1 has 3 OSPF network entries as opposed to 17 using RIP.

Now, you can see why networks are converted from classful routing protocols, such as RIP, to classless protocols, such as OSPF. The migration in this scenario

demonstrates the powerful use of redistribution and what you should be aware of when configuring metrics. Before looking at another scenario, view the full working configurations of all three routers in Figure 8-4.

Example 8-44 displays R1's full working configuration.

Example 8-44 R1's Full Working Configuration

Hostname R1

!

enable password cisco

!

ip subnet-zero interface Loopback0

ip address 141.108.2.1 255.255.255.0

!

interface Loopback1

ip address 141.108.3.1 255.255.255.0

!

interface Loopback2

ip address 141.108.4.1 255.255.255.0

!

interface Loopback3

ip address 141.108.5.1 255.255.255.0

!

interface Loopback4

ip address 141.108.6.1 255.255.255.0

!

interface Loopback5

ip address 141.108.7.1 255.255.255.0

!

interface Loopback6

ip address 141.108.0.1 255.255.255.0

!

interface Ethernet0/0

ip address 141.108.1.1 255.255.255.0

!

interface Serial1/0

ip address 141.108.255.1 255.255.255.252 no ip mroute-cache

no fair-queue clockrate 128000

!

interface Serial1/1

ip address 141.108.255.5 255.255.255.252 clockrate 128000

!

router ospf 1

area 1 range 141.108.0.0 255.255.248.0 network 141.108.0.0 0.0.7.255 area 1 network 141.108.255.0 0.0.0.255 area 0

!

ip classless end

Example 8-45 displays R2's full working configuration.

Example 8-45 R2's Full Working Configuration

hostname R2

!

enable password cisco

!

ip subnet-zero no ip domain-lookup interface Loopback0

ip address 141.108.9.1 255.255.255.0

!

interface Loopback1

ip address 141.108.10.1 255.255.255.0

!

interface Loopback2

ip address 141.108.11.1 255.255.255.0

!

interface Loopback3

ip address 141.108.12.1 255.255.255.0

!

interface Loopback4

ip address 141.108.13.1 255.255.255.0

!

interface Loopback5

ip address 141.108.14.1 255.255.255.0

!

interface Loopback6

ip address 141.108.15.1 255.255.255.0

!

interface Ethernet0/0

ip address 141.108.8.1 255.255.255.0

!

interface TokenRing0/0 no ip address

shutdown

ring-speed 16

!

interface Serial1/0 bandwidth 128

ip address 141.108.255.2 255.255.255.252

!

interface Serial1/1

ip address 141.108.255.10 255.255.255.252

!

router ospf 1

area 2 range 141.108.8.0 255.255.248.0 network 141.108.8.0 0.0.7.255 area 2 network 141.108.255.0 0.0.0.255 area 0

!

ip classless

! end

Example 8-46 displays R3's full working configuration.

Example 8-46 R3's Full Working Configuration

hostname R3

!

enable password cisco

!

no ip domain-lookup

!

interface Loopback0

ip address 141.108.17.1 255.255.255.0

!

interface Loopback1

ip address 141.108.18.1 255.255.255.0

!

interface Loopback2

ip address 141.108.19.1 255.255.255.0

!

interface Loopback3

ip address 141.108.20.1 255.255.255.0

!

interface Loopback4

ip address 141.108.21.1 255.255.255.0

!

interface Loopback5

ip address 141.108.22.1 255.255.255.0

!

interface Loopback6

ip address 141.108.23.1 255.255.255.0

!

interface Ethernet0

ip address 141.108.16.1 255.255.255.0 media-type 10BaseT

!

interface Ethernet1 no ip address

!

interface Serial0

ip address 141.108.255.6 255.255.255.252 bandwidth 125

!

interface Serial1

ip address 141.108.255.9 255.255.255.252 bandwidth 125

clockrate 125000

!

router ospf 1

network 141.108.16.0 0.0.7.255 area 3 network 141.108.255.0 0.0.0.255 area 0 area 3 range 141.108.16.0 255.255.248.0

! end

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