Network Requirements

• R4 functions as ISP router with public IP addresses only
• MGRE environment between R3 (hub) and R5/R6/R7 (spokes)
• OSPF addressing based on 172.16.0.0/16 supernet
• All devices must reach R4's loopback interface
• Optimize LSA updates, accelerate convergence, ensure update security
• Full network reachability

IP Address Planning

Supernet Division

172.16.0.0/16 divided into /19 subnets (3-bit borrowing):

Subnet Allocation Example (Area 0)

• 172.16.0.0/24: P2P links (/30 subnets)
• 172.16.1.0/24: MA networks (/29 subnets)
• 172.16.2.0/24: User networks (loopbacks)
• 172.16.3.0/24: User networks
• 172.16.4.0/24: User networks

Public Network Configuration

R4 (ISP Router)

interface Serial4/0/0
 ip address 34.0.0.2 255.255.255.0
interface Serial4/0/1
 ip address 45.0.0.2 255.255.255.0
interface Serial3/0/0
 ip address 46.0.0.2 255.255.255.0
interface GigabitEthernet0/0/0
 ip address 47.0.0.2 255.255.255.0
interface LoopBack0
 ip address 100.0.0.1 255.255.255.0

Edge Routers (R3, R5, R6, R7)

# R3 Configuration
interface Serial4/0/0
 ip address 34.0.0.1 255.255.255.0
ip route-static 0.0.0.0 0 34.0.0.2

# R5 Configuration
interface Serial4/0/0
 ip address 45.0.0.1 255.255.255.0
ip route-static 0.0.0.0 0 45.0.0.2
interface LoopBack0
 ip address 172.16.2.1 255.255.255.0

# R6 Configuration
interface Serial4/0/0
 ip address 46.0.0.1 255.255.255.0
ip route-static 0.0.0.0 0 46.0.0.2
interface LoopBack0
 ip address 172.16.3.1 255.255.255.0

# R7 Configuration
interface GigabitEthernet0/0/0
 ip address 47.0.0.1 255.255.255.0
ip route-static 0.0.0.0 0 47.0.0.2
interface LoopBack0
 ip address 172.16.4.1 255.255.255.0

MGRE Tunnel Configuration

Hub Router (R3)

interface Tunnel0/0/0
 ip address 172.16.1.1 255.255.255.248
 tunnel-protocol gre p2mp
 source 34.0.0.1
 nhrp entry multicast dynamic
 nhrp network-id 100

Spoke Routers (R5, R6, R7)

# R5 Tunnel Configuration
interface Tunnel0/0/0
 ip address 172.16.1.2 255.255.255.248
 tunnel-protocol gre p2mp
 source Serial4/0/0
 nhrp network-id 100
 nhrp entry 172.16.1.1 34.0.0.1 register

# R6 Tunnel Configuration
interface Tunnel0/0/0
 ip address 172.16.1.3 255.255.255.248
 tunnel-protocol gre p2mp
 source Serial4/0/0
 nhrp network-id 100
 nhrp entry 172.16.1.1 34.0.0.1 register

# R7 Tunnel Configuration
interface Tunnel0/0/0
 ip address 172.16.1.4 255.255.255.248
 tunnel-protocol gre p2mp
 source GigabitEthernet0/0/0
 nhrp network-id 100
 nhrp entry 172.16.1.1 34.0.0.1 register

OSPF Configuration

Area 0 Configuration

# R3 OSPF Configuration
ospf 1 router-id 3.3.3.3
 area 0.0.0.0
  network 172.16.1.1 0.0.0.0
 area 0.0.0.1
  network 172.16.33.3 0.0.0.0
  network 172.16.36.1 0.0.0.0

# R5 OSPF Configuration
ospf 1 router-id 5.5.5.5
 area 0.0.0.0
  network 172.16.2.1 0.极.0.0
  network 172.16.1.2 0.0.0.0

# R6 OSPF Configuration
ospf 1 router-id 6.6.6.6
 area 0.0.0.0
  network 172.16.3.1 0.0.0.0
  network 172.16.1.3 0.0.0.0
 area 0.0.0.2
  network 172.16.64.1 0.0.0.0

# R7 OSPF Configuration
ospf 1 router-id 7.7.7.7
 area 0.0极.0.0
  network 172.16.4.1 0.0.0.0
  network 172.16.1.4 0.0.0.0
 area 0.0.0.3
  network 172.16.96.1 0.0.0.0

Tunnel Interface Network Type Modification

# All tunnel interfaces must be set to P2MP network type
interface Tunnel0/0/0
 ospf network-type p2mp

Area 1 Configuration

# R1 OSPF Configuration
ospf 1 router-id 1.1.1.1
 area 0.0.0.1
  network 172.16.32.0 0.0.31.255

# R2 OSPF Configuration
ospf 1 router-id 2.2.2.2
 area 0.0.0.1
  network 172.16.32.0 0.0.31.255

RIP Configuration and Redistribution

# R12 RIP Configuration
rip
 network 172.16.0.0

# RIP to OSPF Redistribution
ospf 1
 import-route rip

Multi-Process OSPF for Area 4

# R9 Multi-Process Configuration
ospf 2 router-id 9.9.9.9
 area 0.0.0.0
  network 172.16.128.0 0.0.31.255

ospf 1
 import-route ospf 2

ospf 2
 import-route ospf 1

# R10 OSPF Configuration
ospf 2 router-id 10.1.1.1
 area 极.0.0.0
  network 172.16.128.0 极.0.31.255

Verification and Testing

• Verify OSPF neighbor relationships using display ospf peer
• Check routing table completeness with display ip routing-table
• Test end-to-end connectivity between all network segments
• Validate MGRE tunnel functionality and reachability
• Confirm proper redistribution between OSPF areas and RIP