GNS3 - VitualBox Part 2: Creating an OSPF Backbone Area

Configuring four Cisco 7206 routers connected by OC-3 and T-1 lines to act as an OSPF Backbone Area.  This article starts using the Basic Topology configured in Part 1 of the series.

Introduction

The illustration above depicts what will be configured: four Cisco 7206 routers (Coudersport, Philadelphia, Pittsburgh and Harrisburg).  The Coudersport router is connected to the other three using point-to-point OC-3 lines; the remaining three links between Philadelphia, Pittsburgh and Harrisburg are point-to-point T-1 lines.

The LAN side of each router consists of two Fast Ethernet adapters, one configured with addresses in the OSPF Backbone Area 0.0.0.0 (address range 172.16.0.0 - 172.16.31.255) and the other defining a private network in the 10.x.x.x address range.

Specific details of network addressing are presented in the figure above.

Adding the Cisco Routers

There are two new 7206 routers (Pittsburgh and Harrisburg) added to the existing two in the network (Coudersport and Philadelphia).  All routers are provided a C-7200-IO-2FE card in slot 0 (two Fast Ethernet adapters).  The existing Coudersport and Philadelphia routers have PA-POS-OC3 cards in slot 6 (one OC-3 adapter).

The Coudersport router requires two additional adapters to support the topology: PA-POS-OC3 cards in slots 4 and 5.  The Philadelphia router requires one additional adapter to support the topology: a PA-4T+ card in slot 1 (four T-1 adapters). The Pittsburgh and Harrisburg routers are equipped identically to the Philadelphia router: a PA-4T+ card in slot 1 and a PA-POS-OC3 card in slot 6.

Note the distribution of cards.  The Cisco 7206 has two PCI buses bridged into the system bus, with slots 0, 1, 3 and 5 on one PCI bus and slots 2, 4 and 6 on the other.  The distribution specified spreads the high-speed interfaces (Fast Ethernet and OC-3) among the two PCI buses.  Detailed instructions for calculating allowable card configurations are available from Cisco's 7200 Port Adapter Configuration Guidelines.

Router Configurations

The following sections present those parts of the router configurations that define address and OSPF information.

Coudersport 7206 (COU_7206)

interface FastEthernet0/0
 ip address 172.16.254.1 255.255.255.0
 duplex full
 speed auto
!
interface FastEthernet0/1
 ip address 10.0.0.1 255.255.255.0
 duplex full
 speed auto
!
interface POS4/0
 ip address 172.16.0.9 255.255.255.252
!
interface POS5/0
 ip address 172.16.0.5 255.255.255.252
!
interface POS6/0
 ip address 172.16.0.1 255.255.255.252
!
router ospf 1
 router-id 10.0.0.1
 log-adjacency-changes
 area 0.0.0.0 range 172.16.0.0 255.240.0.0
 area 10.0.0.0 range 10.0.0.0 255.255.0.0
 network 10.0.0.0 0.0.0.255 area 10.0.0.0
 network 172.16.0.0 0.0.0.3 area 0.0.0.0
 network 172.16.0.4 0.0.0.3 area 0.0.0.0
 network 172.16.0.8 0.0.0.3 area 0.0.0.0
 network 172.16.254.0 0.0.0.255 area 0.0.0.0
!

Philadelphia 7206 (PHL_7206)

interface FastEthernet0/0
 ip address 172.16.253.1 255.255.255.0
 duplex full
 speed auto
!
interface FastEthernet0/1
 ip address 10.64.0.1 255.255.255.0
 duplex full
 speed auto
!
interface Serial1/0
 ip address 172.16.1.1 255.255.255.252
 serial restart-delay 0
!
interface Serial1/1
 ip address 172.16.1.5 255.255.255.252
 serial restart-delay 0
[...]
!
interface POS6/0
 ip address 172.16.0.2 255.255.255.252
!
router ospf 1
 router-id 10.64.0.1
 log-adjacency-changes
 area 0.0.0.0 range 172.16.0.0 255.240.0.0
 area 10.64.0.0 range 10.64.0.0 255.255.0.0
 area 10.64.0.0 virtual-link 10.64.0.3
 network 10.64.0.0 0.0.0.255 area 10.64.0.0
 network 172.16.0.0 0.0.0.3 area 0.0.0.0
 network 172.16.1.0 0.0.0.3 area 0.0.0.0
 network 172.16.1.4 0.0.0.3 area 0.0.0.0
 network 172.16.253.0 0.0.0.255 area 0.0.0.0
!

Pittsburgh 7206 (PIT_7206)

interface FastEthernet0/0
 ip address 172.16.252.1 255.255.255.0
 duplex full
 speed auto
!
interface FastEthernet0/1
 ip address 10.128.0.1 255.255.255.0
 duplex full
 speed auto
!
interface Serial1/0
 ip address 172.16.1.2 255.255.255.252
 serial restart-delay 0
!
interface Serial1/1
 ip address 172.16.1.9 255.255.255.252
 serial restart-delay 0
[...]
!
interface POS6/0
 ip address 172.16.0.6 255.255.255.252
!
router ospf 1
 router-id 10.128.0.1
 log-adjacency-changes
 area 0.0.0.0 range 172.16.0.0 255.240.0.0
 area 10.128.0.0 range 10.128.0.0 255.255.0.0
 network 10.128.0.0 0.0.0.255 area 10.128.0.0
 network 172.16.0.4 0.0.0.3 area 0.0.0.0
 network 172.16.1.0 0.0.0.3 area 0.0.0.0
 network 172.16.1.8 0.0.0.3 area 0.0.0.0
 network 172.16.252.0 0.0.0.255 area 0.0.0.0
!

Harrisburg 7206 (HBG_7206)

interface FastEthernet0/0
 ip address 172.16.251.1 255.255.255.0
 duplex full
 speed auto
!
interface FastEthernet0/1
 ip address 10.192.0.1 255.255.255.0
 duplex full
 speed auto
!
interface Serial1/0
 ip address 172.16.1.6 255.255.255.252
 serial restart-delay 0
!
interface Serial1/1
 ip address 172.16.1.10 255.255.255.252
 serial restart-delay 0[...]
!
interface POS6/0
 ip address 172.16.0.10 255.255.255.252
!
router ospf 1
 router-id 10.192.0.1
 log-adjacency-changes
 area 0.0.0.0 range 172.16.0.0 255.240.0.0
 area 10.192.0.0 range 10.192.0.0 255.255.0.0
 network 19.192.0.0 0.0.0.255 area 10.192.0.0
 network 172.16.0.8 0.0.0.3 area 0.0.0.0
 network 172.16.1.4 0.0.0.3 area 0.0.0.0
 network 172.16.1.8 0.0.0.3 area 0.0.0.0
 network 172.16.251.0 0.0.0.255 area 0.0.0.0
!

Checking the Configuration

Upon configuring the routers, each will:

1. Have a default gateway that routes through the Coudersport Gateway Debian Linux server
2. Have routing table entries for all networks in the OSPF Backbone network
3. Have a routing table entry for its own 10.x.x.x network
4. Have routing table summary entries for the three other 10.x.x.x networks
5. Have OSPF Neighbor entries for the three other Cisco 7206 routers
6. Be able to ping public IP addresses (e.g. 8.8.8.8)

The video below depicts the process described above.