# Point-to-Multipoint OSPF in Metro Ethernet WAN Network
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`
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