Sign in Subscribe
Cisco

Cisco CCNP - OSPF Multi Area - Lab 2

This lab will explore the key features of an OSPF multi-area network. The lab on the link below is a prerequisite. This link provides further explanation on OSPF Multi Area networks.

Cisco CCNP - OSPF Single Area - Lab 1
This article will describe the first CCNP MPLS lab. Initial Configuration Lab Details The simulator used for this article was PNETLAB and the devices are running the Cisco IOSv image. Getting Command Line Access Answer no to the initial configuration dialogue. % Please answer ‘yes’ or ‘no’. Would you like to
Infoitech - [B]loggingTiago Stoco

Lab Description

Diagram

Area 0 is the backbone to which all other areas should connect.

Area 20 (Normal)

This lab assumes you are already familiar with the basic configuration of Cisco devices learned in the required OSPF single-area lab.

Area 20 will be configured as a normal area.

R4 - OSPF Configuration

Let's configure OSPF on the R4 interface gigabitEthernet 0/0 connected to R2.

configure terminal
router ospf 1
bfd all-interfaces

Enabling OSPF and BFD

area 20 authentication message-digest
exit

Enabling OSPF Authentication in Area 20

configure terminal
interface Loopback0
ip address 10.0.0.4 255.255.255.255
ip ospf message-digest-key 1 md5 cisco_ospf
ip ospf network point-to-point
ip ospf 1 area 20

Configuring the Loopback interface.

interface gigabitEthernet0/0
description "R4 to R2"
ip address 10.2.4.4 255.255.255.0
ip ospf message-digest-key 1 md5 cisco_ospf
ip ospf network point-to-point
ip ospf 1 area 20
bfd interval 300 min_rx 300 multiplier 3

Configuring OSPF Area 20 and BFD

R2 - OSPF Configuration
router ospf 1
area 20 authentication message-digest

Enabling authentication within area20

interface GigabitEthernet0/2
description "R2 to R4"
ip address 10.2.4.2 255.255.255.0
ip ospf message-digest-key 1 md5 cisco_ospf
ip ospf network point-to-point
ip ospf 1 area 20
bfd interval 300 min_rx 300 multiplier 3

Configuring OSPF Area 20 and BFD

OSPF Adjacency

We can now check the OSPF adjacency and LSAs received from R2 with the below commands.

The output shows us that R2 is an Area Border Router (ABR) meaning that it has interfaces configured in more than one area. In our example R2 is connected to Area 0 and Area 20.

show ip ospf database router

            OSPF Router with ID (10.0.0.4) (Process ID 1)

		Router Link States (Area 20)

  LS age: 1319
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 10.0.0.2
  Advertising Router: 10.0.0.2
  LS Seq Number: 80000002
  Checksum: 0xEEE9
  Length: 48
  Area Border Router
  Number of Links: 2

    Link connected to: another Router (point-to-point)
     (Link ID) Neighboring Router ID: 10.0.0.4
     (Link Data) Router Interface address: 10.2.4.2
      Number of MTID metrics: 0
       TOS 0 Metrics: 1

    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 10.2.4.0
     (Link Data) Network Mask: 255.255.255.0
      Number of MTID metrics: 0
       TOS 0 Metrics: 1
          
          
  LS age: 1318
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 10.0.0.4
  Advertising Router: 10.0.0.4
  LS Seq Number: 80000002
  Checksum: 0x2A8C
  Length: 60
  Number of Links: 3
          
    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 10.0.0.4
     (Link Data) Network Mask: 255.255.255.255
      Number of MTID metrics: 0
       TOS 0 Metrics: 1
          
    Link connected to: another Router (point-to-point)
     (Link ID) Neighboring Router ID: 10.0.0.2
     (Link Data) Router Interface address: 10.2.4.4
      Number of MTID metrics: 0
       TOS 0 Metrics: 1
          
    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 10.2.4.0
     (Link Data) Network Mask: 255.255.255.0
      Number of MTID metrics: 0
       TOS 0 Metrics: 1

R4 - OSPF Router LSA (Type 1)

The ABR router (R2) issued summary LSAs to every destination in Area 1.

show ip ospf database summary 
            OSPF Router with ID (10.0.0.4) (Process ID 1)

		Summary Net Link States (Area 20)

  LS age: 887
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 10.0.0.1 (summary Network Number)
  Advertising Router: 10.0.0.2
  LS Seq Number: 8000000B
  Checksum: 0x9683
  Length: 28
  Network Mask: /32
	MTID: 0 	Metric: 2 

  LS age: 887
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 10.0.0.2 (summary Network Number)
  Advertising Router: 10.0.0.2
  LS Seq Number: 8000000B
  Checksum: 0x8297
  Length: 28
  Network Mask: /32
        MTID: 0 	Metric: 1 
          
  LS age: 887
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 10.0.0.3 (summary Network Number)
  Advertising Router: 10.0.0.2
  LS Seq Number: 8000000B
  Checksum: 0x8295
  Length: 28
  Network Mask: /32
        MTID: 0 	Metric: 2 
          
  LS age: 887
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 10.1.2.0 (summary Network Number)
  Advertising Router: 10.0.0.2
  LS Seq Number: 8000000B
  Checksum: 0x74A4
  Length: 28
  Network Mask: /24
        MTID: 0 	Metric: 1 
          
  LS age: 887
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 10.1.3.0 (summary Network Number)
  Advertising Router: 10.0.0.2
  LS Seq Number: 8000000B
  Checksum: 0x73A3
  Length: 28
  Network Mask: /24
        MTID: 0 	Metric: 2 
          
  LS age: 887
  Options: (No TOS-capability, DC, Upward)
  LS Type: Summary Links(Network)
  Link State ID: 10.2.3.0 (summary Network Number)
  Advertising Router: 10.0.0.2
  LS Seq Number: 8000000B
  Checksum: 0x5DB9
  Length: 28
  Network Mask: /24
        MTID: 0 	Metric: 1

R4 - OSPF Summary LSA (Type 3)

The OSPF routes learned can be checked with the command below.

show ip route ospf 

Codes: O - OSPF, IA - OSPF inter area 
     
Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O IA     10.0.0.1/32 [110/3] via 10.2.4.2, 1d00h, GigabitEthernet0/0
O IA     10.0.0.2/32 [110/2] via 10.2.4.2, 1d00h, GigabitEthernet0/0
O IA     10.0.0.3/32 [110/3] via 10.2.4.2, 1d00h, GigabitEthernet0/0
O IA     10.1.2.0/24 [110/2] via 10.2.4.2, 1d00h, GigabitEthernet0/0
O IA     10.1.3.0/24 [110/3] via 10.2.4.2, 1d00h, GigabitEthernet0/0
O IA     10.2.3.0/24 [110/2] via 10.2.4.2, 1d00h, GigabitEthernet0/0

R4 - OSPF Routes.

Area 40 (Stub)

Stub areas have a Summary LSA for the default route flooded into the area and installed in the route-table of the intra-area routers in the stub area.

R7 - OSPF Configuration

Let's configure OSPF on the R7 interfaces and the OSPF process itself. 

configure terminal
router ospf 1
bfd all-interfaces

Enabling OSPF and BFD

area 40 authentication message-digest
area 40 stub
exit

Configuring OSPF Area 40 as stub.

It is important to note that Area 40 is configured as STUB.

interface Loopback0
ip address 10.0.0.7 255.255.255.255
ip ospf message-digest-key 1 md5 cisco_ospf
ip ospf network point-to-point
ip ospf 1 area 40

Configuring the Loopback interface.

interface GigabitEthernet0/0
description "R7 to R3"
ip address 192.168.3.7 255.255.255.0
ip ospf message-digest-key 1 md5 cisco_ospf
ip ospf network point-to-point
ip ospf 1 area 40
bfd interval 600 min_rx 600 multiplier 3

Configuring the interface facing R3.

R3 - OSPF Configuration
configure terminal
router ospf 1
area 40 authentication message-digest
area 40 stub
exit

Configuring OSPF Area 40 as stub.

We need to match the config with R7 and the Area should be configured as STUB.

interface GigabitEthernet0/2
description "R3 to R7"
ip address 192.168.3.3 255.255.255.0
ip ospf message-digest-key 1 md5 cisco_ospf
ip ospf network point-to-point
ip ospf 1 area 40
bfd interval 600 min_rx 600 multiplier 3

Configuring OSPF Area 40 and BFD

OSPF Adjacency

With the below commands, we can now check the OSPF adjacency and LSAs received from the ABR R3.

The outputs below show us the LSAs flooded by R3. The LSAs are Type 1 (Router), Type 3 (Summary).

show ip ospf database 
            OSPF Router with ID (10.0.0.7) (Process ID 1)

		Router Link States (Area 40)

Link ID         ADV Router      Age         Seq#       Checksum Link count
10.0.0.3        10.0.0.3        1876        0x80000085 0x003E5A 2
10.0.0.7        10.0.0.7        175         0x8000008A 0x004E1C 3

		Summary Net Link States (Area 40)

Link ID         ADV Router      Age         Seq#       Checksum
0.0.0.0         10.0.0.3        1876        0x80000008 0x0037F2
10.0.0.1        10.0.0.3        1876        0x80000084 0x00C5DA
10.0.0.2        10.0.0.3        1876        0x80000084 0x00B1EE
10.0.0.3        10.0.0.3        1876        0x80000084 0x009D03
10.0.0.4        10.0.0.3        1876        0x80000084 0x00A7F5
10.1.2.0        10.0.0.3        1876        0x80000084 0x00A3FB
10.1.3.0        10.0.0.3        1876        0x80000084 0x008E11
10.2.3.0        10.0.0.3        1876        0x80000084 0x00821C
10.2.4.0        10.0.0.3        1876        0x80000084 0x00811B

A default route is flooded into the area by the ABR.

show ip route
Codes: L - local, C - connected, S - static, O - OSPF, IA - OSPF inter area 
Gateway of last resort is 192.168.3.3 to network 0.0.0.0

O*IA  0.0.0.0/0 [110/2] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
      10.0.0.0/8 is variably subnetted, 9 subnets, 2 masks
O IA     10.0.0.1/32 [110/4] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
O IA     10.0.0.2/32 [110/3] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
O IA     10.0.0.3/32 [110/2] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
O IA     10.0.0.4/32 [110/4] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
C        10.0.0.7/32 is directly connected, Loopback0
O IA     10.1.2.0/24 [110/3] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
O IA     10.1.3.0/24 [110/2] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
O IA     10.2.3.0/24 [110/2] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
O IA     10.2.4.0/24 [110/3] via 192.168.3.3, 04:33:30, GigabitEthernet0/0
      192.168.3.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.3.0/24 is directly connected, GigabitEthernet0/0
L        192.168.3.7/32 is directly connected, GigabitEthernet0/0

R7 routing table.

Read next