Point-to-Multipoint OSPF in Metro Ethernet WAN Network

Nerd Cafe

As a CCNA instructor, I'll guide you through configuring a point-to-multipoint (P2MP) OSPF network in this Metro Ethernet WAN scenario. This topology shows a hub-and-spoke design with Tehran HQ-Router as the hub and three branch routers as spokes.

Understanding the Topology

Topology

From the image, we can see:

• OSPF Area 0 is the backbone area

• HQ-Router is the hub with three subinterfaces (VLANs 10, 20, 30)

• Three branch routers (Shiraz, Mashhad, Tabriz) connect to the hub via Metro Ethernet

• The ISP provides the Metro Ethernet service

Point-to-Multipoint Network Characteristics

P2MP is ideal for this scenario because:

1. It's a hub-and-spoke topology

2. All spokes connect to a single hub interface (logically)

3. We want to treat the WAN like a multi-access network

4. It avoids the need for full mesh connectivity

Configuration Steps

1. Configure the HQ-Router (Hub)

HQ-Router#configure terminal
HQ-Router(config)#interface fastEthernet 0/0
HQ-Router(config-if)#no shutdown                                                                                      et0/0, changed state to up
HQ-Router(config-if)#exit
HQ-Router(config)#interface fastEthernet 0/0.1
HQ-Router(config-subif)#encapsulation dot1Q 10
HQ-Router(config-subif)#ip address 192.168.10.1 255.255.255.0
HQ-Router(config-subif)#ip ospf network point-to-multipoint
HQ-Router(config-subif)#exit
HQ-Router(config)#interface fastEthernet 0/0.2
HQ-Router(config-subif)#encapsulation dot1Q 20
HQ-Router(config-subif)#ip address 192.168.20.1 255.255.255.0
HQ-Router(config-subif)#ip ospf network point-to-multipoint
HQ-Router(config-subif)#exit
HQ-Router(config)#interface fastEthernet 0/0.3
HQ-Router(config-subif)#encapsulation dot1Q 30
HQ-Router(config-subif)#ip address 192.168.30.1 255.255.255.0
HQ-Router(config-subif)#ip ospf network point-to-multipoint
HQ-Router(config-subif)#exit
HQ-Router(config)#router ospf 1
HQ-Router(config-router)#net
HQ-Router(config-router)#network 192.168.10.0 0.0.0.255 area 0
HQ-Router(config-router)#network 192.168.20.0 0.0.0.255 area 0
HQ-Router(config-router)#network 192.168.30.0 0.0.0.255 area 0
HQ-Router(config-router)#^Z
HQ-Router#write memory

2. Configure Shiraz (Branch-1)

Branch-1#configure terminal
Branch-1(config)#interface fastEthernet 0/0
Branch-1(config-if)#ip address 192.168.10.2 255.255.255.0
Branch-1(config-if)#ip ospf network point-to-multipoint
Branch-1(config-if)#no shutdown
Branch-1(config-if)#exit
Branch-1(config)#router ospf 1
Branch-1(config-router)#network 192.168.10.0 0.0.0.255 area 0
Branch-1(config-router)#^Z
Branch-1#write memory

3. Configure Mashhad (Branch-2)

Branch-2#configure terminal
Branch-2(config)#interface fastEthernet 0/0
Branch-2(config-if)#ip address 192.168.20.2 255.255.255.0
Branch-2(config-if)#ip ospf network point-to-multipoint
Branch-2(config-if)#no shutdown
Branch-2(config-if)#exit
Branch-2(config)#router ospf 1
Branch-2(config-router)#network 192.168.20.0 0.0.0.255 area 0
Branch-2(config-router)#^Z
Branch-2#write memory

4. Configure Tabriz (Branch-3)

Branch-3#configure terminal
Branch-3(config)#interface fastEthernet 0/0
Branch-3(config-if)#ip address 192.168.30.2 255.255.255.0
Branch-3(config-if)#ip ospf network point-to-multipoint
Branch-3(config-if)#no shutdown
Branch-3(config-if)#exit
Branch-3(config)#router ospf 1
Branch-3(config-router)#network 192.168.30.0 0.0.0.255 area 0
Branch-3(config-router)#^Z
Branch-3#write memory

5. ISP Configuration (Metro Ethernet Switch)

ISP#configure terminal
ISP(config)#vlan 10
ISP(config-vlan)#name BRANCH-1
ISP(config-vlan)#exit
ISP(config)#vlan 20
ISP(config-vlan)#name BRANCH-2
ISP(config-vlan)#exit
ISP(config)#vlan 30
ISP(config-vlan)#name BRANCH-3
ISP(config-vlan)#exit
ISP(config)#interface ethernet 0/0
ISP(config-if)#desc
ISP(config-if)#description TRUNK-TO-HQ-ROUTER
ISP(config-if)#switchport trunk encapsulation dot1q
ISP(config-if)#switchport mode trunk
ISP(config-if)#exit
ISP(config)#interface ethernet 0/1
ISP(config-if)#description BRANCH-1
ISP(config-if)#switchport mode access
ISP(config-if)#switchport access vlan 10
ISP(config-if)#exit
ISP(config)#interface ethernet 0/2
ISP(config-if)#description BRANCH-2
ISP(config-if)#switchport mode access
ISP(config-if)#switchport access vlan 20
ISP(config-if)#exit
ISP(config)#interface ethernet 0/3
ISP(config-if)#description BRANCH-3
ISP(config-if)#switchport mode access
ISP(config-if)#switchport access vlan 30
ISP(config-if)#^Z
ISP#write memory

Verify IP Connectivity (ping between devices)

• HQ-Router

HQ-Router#ping 192.168.10.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.10.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/20/28 ms
HQ-Router#ping 192.168.20.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.20.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/19/28 ms
HQ-Router#ping 192.168.30.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.30.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/16/24 ms
HQ-Router#

• Branch-1 Router

Branch-1#ping 192.168.20.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.20.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/27/36 ms
Branch-1#ping 192.168.30.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.30.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/17/28 ms
Branch-1#

• Branch-2 Router

Branch-2#ping 192.168.30.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.30.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/26/40 ms
Branch-2#

Keywords

OSPF, Point-to-Multipoint, Metro Ethernet, Hub-and-Spoke, NBMA, DR/BDR, Subinterfaces, Cisco Configuration, Routing Protocol, WAN, VLAN, OSPF Neighbors, Multicast, Non-Broadcast, Hello Timers, IP Subnetting, Network Design, Scalability, Troubleshooting, Best Practices, سیسکو