My laboratory objectives are as follows:

1.    Configured and enable OSPF as per the topology. This can be verified when the adjacencies were formed.

2. Verify that Sydney and Auckland will be the DR on the broadcast network where they are connected with.

3.  Verify from Manila Router that LSDB will have a details of the networks 50.50.50.0/24 and 60.60.60.0/24 advertised by Singapore and Auckland but the routing table will not show this subnets.

4. Enable Virtual-Links to established the connectivity between Sydney and Auckland.

5. Verify that the LSDB of Sydney does not have the networks that belongs to Singapore and Auckland Loopback interfaces and vice-versa. But proved that the routing table of Sydney or Auckland have this Loopback address.

6. Verify the connectivity after enabling the Virtual-Links.

Here are my router configurations:

Manila#sh run | sec ospf
router ospf 1
 router-id 11.11.11.11
 network 10.10.10.0 0.0.0.255 area 1
 network 192.168.12.0 0.0.0.255 area 1
 network 192.168.13.0 0.0.0.255 area 0
Manila#


Melbourne#sh run | sec ospf
router ospf 1
 router-id 22.22.22.22
 network 20.20.20.0 0.0.0.255 area 1
 network 192.168.12.0 0.0.0.255 area 1
 network 192.168.25.0 0.0.0.255 area 0
Melbourne#


 Perth#sh run | sec ospf
router ospf 1
 router-id 33.33.33.33
 network 0.0.0.0 255.255.255.255 area 0
Perth#


 Sydney#sh run | sec ospf
router ospf 1
 router-id 44.44.44.44
 network 0.0.0.0 255.255.255.255 area 0
Sydney#

Singapore#sh run | sec ospf
router ospf 1
 router-id 55.55.55.55
 network 0.0.0.0 255.255.255.255 area 0
Singapore#

 VERIFICATIONS:
 

1. I have simplified the configurations for Router’s  Perth, Sydney, Singapore & Auckland by just advertising any IP address under OSPF process since all of them are in Area 0.

2. Let’s check the adjacencies of the routers.

Perth#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
11.11.11.11       0   FULL/  –        00:00:33    192.168.13.1    Serial3/1
44.44.44.44       1   FULL/DR         00:00:33    192.168.34.4    FastEthernet0/0
Perth#

Sydney#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
33.33.33.33       1   FULL/BDR        00:00:34    192.168.34.3    FastEthernet0/0
Sydney#

Observation:

a. The results above shows that Sydney were elected as the DR on the the broadcast network towards Perth.

b  Also we know that adjacencies were formed between Perth to Manila router via a point-to-point link.

Manila#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
33.33.33.33       0   FULL/  –        00:00:32    192.168.13.3    Serial3/1
22.22.22.22       0   FULL/  –        00:00:30    192.168.12.2    Serial3/0
Manila#

Melbourne#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
55.55.55.55       0   FULL/  –        00:00:32    192.168.25.5    Serial3/1
11.11.11.11       0   FULL/  –        00:00:33    192.168.12.1    Serial3/0
Melbourne#

Observation:

a. Adjacencies were formed as per our topology above. All are are Point-to-Point link.

Melbourne#sh ip ospf interface ser3/0
Serial3/0 is up, line protocol is up
  Internet Address 192.168.12.2/24, Area 1, Attached via Network Statement
  Process ID 1, Router ID 22.22.22.22, Network Type POINT_TO_POINT, Cost: 64
  Topology-MTID    Cost    Disabled    Shutdown      Topology Name
        0           64        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_POINT
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

Singapore#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
22.22.22.22       0   FULL/  –        00:00:31    192.168.25.2    Serial3/1
66.66.66.66       1   FULL/DR         00:00:36    192.168.56.6    FastEthernet0/0
Singapore#


 Auckland#show ip ospf neighbor

Neighbor ID     Pri   State           Dead Time   Address         Interface
55.55.55.55       1   FULL/BDR        00:00:33    192.168.56.5    FastEthernet0/0
Auckland#

Observation:

a. The results above shows that Auckland were elected as the DR on the the broadcast network towardsSingapore

b.  Also we know that adjacencies were formed between Singapore to Melbourne router via a point-to-point link.

3. Now, let’s verify the Routing tables.

Manila#show ip route ospf

      20.0.0.0/32 is subnetted, 1 subnets
O        20.20.20.1 [110/65] via 192.168.12.2, 00:54:52, Serial3/0
      30.0.0.0/32 is subnetted, 1 subnets
O        30.30.30.1 [110/65] via 192.168.13.3, 00:15:04, Serial3/1
      40.0.0.0/32 is subnetted, 1 subnets
O        40.40.40.1 [110/66] via 192.168.13.3, 00:15:04, Serial3/1
O     192.168.34.0/24 [110/65] via 192.168.13.3, 00:15:04, Serial3/1
Manila#

Observation: 

a. This means that from Manila router, I should be able to reach Perth and Sydney.

Manila#ping 40.40.40.1 source 192.168.12.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 40.40.40.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.12.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 324/369/436 ms

Manila#ping 30.30.30.1 source 192.168.12.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 30.30.30.1, timeout is 2 seconds:
Packet sent with a source address of 192.168.12.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 164/227/300 ms

4.  Again if we have to look into the OSPF database of Manila, We can see the Type 3 Summary LSA’s for both Area 1 and Area 0 that includes the networks that belongs to Melbourne, Singapore and Auckland. But the routing table on Manila are not showing this networks.  Lets take a look for example the network 60.60.60.0/24. As we can see from the  Summary Net Link States (Area 1), it’s advertise by Melbourne Router (22.22.22.22). Melbourne is advertising the same LSA to Manila’s as they are on the same OSPF domain which is Area 1. We know that all routers within the same OSPF domain need to have the same database topology  This principle has to be remembered. We have just seen that Area 1 and Area 2 cannot talk to one another but Area 0 routers can.  Make sense?

 
Manila#show ip ospf database

Link ID         ADV Router      Age         Seq#       Checksum
30.30.30.1      11.11.11.11     1247        0x80000004 0x007EF2
40.40.40.1      11.11.11.11     1064        0x80000004 0x001F33
50.50.50.1      22.22.22.22     1524        0x80000002 0x0064A6
60.60.60.1      22.22.22.22     1033        0x80000002 0x0005E6
192.168.13.0    11.11.11.11     1570        0x80000002 0x007DDB
192.168.25.0    22.22.22.22     1524        0x80000002 0x00AD73
192.168.34.0    11.11.11.11     1247        0x80000004 0x009BA5
192.168.56.0    22.22.22.22     1524        0x80000002 0x00619F
Manila#
5. Now, let’s create the Virtual-Links between Manila and Melbourne. Remember, our objective is to established communications between Sydney and Auckland routers. 

Manila(config)#router ospf 1
Manila(config-router)#area 1 virtual-link 22.22.22.22
Manila(config-router)#

<< As I'm entering the above commands on Manila router, Melbourne router have shown the logs below,

Melbourne#
*Aug  5 13:51:19.887: %OSPF-4-ERRRCV: Received invalid packet: mismatched area ID, from backbone area must be virtual-link but not found from 192.168.12.1, Serial3/0

Now, let me enable the same in Melbourne router,

Melbourne(config)#router ospf 1
Melbourne(config-router)#area 1 virtual-link 11.11.11.11
Melbourne(config-router)#^Z

Melbourne#
*Aug  5 13:51:42.315: %SYS-5-CONFIG_I: Configured from console by console
*Aug  5 13:51:42.695: %OSPF-5-ADJCHG: Process 1, Nbr 11.11.11.11 on OSPF_VL0 from LOADING to FULL, Loading Done

Manila(config-router)#
*Aug  5 13:51:31.887: %OSPF-5-ADJCHG: Process 1, Nbr 22.22.22.22 on OSPF_VL0 from LOADING to FULL, Loading Done
Manila(config-router)#
 
Observation:

a. So As we can see, the adjacencies were formed between the Virtual links that is created between Manila and Melbourne. In this scenario, I have OSPF_VL0 created in both Melbourne and Manila.

 Let’s check the virtual links using the command ” show ip ospf virtual-link “

Manila#show ip ospf virtual-links
Virtual Link OSPF_VL0 to router 22.22.22.22 is up
  Run as demand circuit
  DoNotAge LSA allowed.
  Transit area 1, via interface Serial3/0
 Topology-MTID    Cost    Disabled     Shutdown      Topology Name
        0           64        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:04
    Adjacency State FULL (Hello suppressed)
    Index 2/3, retransmission queue length 0, number of retransmission 0
    First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
    Last retransmission scan length is 0, maximum is 0
    Last retransmission scan time is 0 msec, maximum is 0 msec
 
Melbourne#sh ip ospf virtual-links
Virtual Link OSPF_VL0 to router 11.11.11.11 is up
  Run as demand circuit
  DoNotAge LSA allowed.
  Transit area 1, via interface Serial3/0
 Topology-MTID    Cost    Disabled     Shutdown      Topology Name
        0           64        no          no            Base
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:00
    Adjacency State FULL (Hello suppressed)
    Index 2/3, retransmission queue length 0, number of retransmission 0
    First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)
    Last retransmission scan length is 0, maximum is 0
    Last retransmission scan time is 0 msec, maximum is 0 msec
Melbourne#
Observation:

a.  So as we see above, the Virtual-Links were up and details of the following were shown,

   Virtual Link Interface – VL0
   Transit Area = 1 ( Area 1)
   Hello timer = 10 ( default for Point-to-Point)
   Dead Interval Timer = 40 ( it’s 4 x the Hello timer)

6. Let’s check now the content of the routing table. I want to go straight by checking the Auckland and Sydney router.

Auckland#show ip route ospf
Gateway of last resort is not set

      10.0.0.0/32 is subnetted, 1 subnets
O IA     10.10.10.1 [110/130] via 192.168.56.5, 00:54:08, FastEthernet0/0
      20.0.0.0/32 is subnetted, 1 subnets
O IA     20.20.20.1 [110/66] via 192.168.56.5, 00:54:08, FastEthernet0/0
      30.0.0.0/32 is subnetted, 1 subnets
O        30.30.30.1 [110/194] via 192.168.56.5, 00:11:09, FastEthernet0/0
      40.0.0.0/32 is subnetted, 1 subnets
O        40.40.40.1 [110/195] via 192.168.56.5, 00:11:09, FastEthernet0/0
      50.0.0.0/32 is subnetted, 1 subnets
O        50.50.50.1 [110/2] via 192.168.56.5, 00:54:08, FastEthernet0/0
O IA  192.168.12.0/24 [110/129] via 192.168.56.5, 00:54:08, FastEthernet0/0
O     192.168.13.0/24 [110/193] via 192.168.56.5, 00:11:09, FastEthernet0/0
O     192.168.25.0/24 [110/65] via 192.168.56.5, 00:54:08, FastEthernet0/0
O     192.168.34.0/24 [110/194] via 192.168.56.5, 00:11:09, FastEthernet0/0
Auckland#


Observation: 

a. Sydney loopback (40.40.40.0/24) and Perth Loopback (30.30.30.0/24) were already installed on Auckland router. But why it does not appear on the OSPF database on Auckland routers? I would say this will not appear as well in Singapore router LSDB.

Auckland#show ip ospf database

Link ID         ADV Router      Age         Seq#       Checksum
10.10.10.1      11.11.11.11     1112  (DNA) 0x80000003 0x00D01E
10.10.10.1      22.22.22.22     1729        0x80000003 0x00087A
20.20.20.1      11.11.11.11     1112  (DNA) 0x80000003 0x00E9A6
20.20.20.1      22.22.22.22     1729        0x80000003 0x001C88
192.168.12.0    11.11.11.11     1112  (DNA) 0x80000003 0x0086D2
192.168.12.0    22.22.22.22     1729        0x80000003 0x003BF1

 Singapore#show ip ospf database

Link ID         ADV Router      Age         Seq#       Checksum
10.10.10.1      11.11.11.11     1111  (DNA) 0x80000003 0x00D01E
10.10.10.1      22.22.22.22     95          0x80000004 0x00067B
20.20.20.1      11.11.11.11     1111  (DNA) 0x80000003 0x00E9A6
20.20.20.1      22.22.22.22     95          0x80000004 0x001A89
192.168.12.0    11.11.11.11     1111  (DNA) 0x80000003 0x0086D2
192.168.12.0    22.22.22.22     95          0x80000004 0x0039F2
Singapore#
 But let’s check the Melbourne router LSDB.


Melbourne#show ip ospf database

Link ID         ADV Router      Age         Seq#       Checksum
30.30.30.1      11.11.11.11     1808        0x80000005 0x007CF3
40.40.40.1      11.11.11.11     1551        0x80000005 0x001D34
50.50.50.1      22.22.22.22     42          0x80000004 0x0060A8
60.60.60.1      22.22.22.22     1524        0x80000003 0x0003E7
192.168.13.0    11.11.11.11     11          0x80000004 0x0079DD
192.168.25.0    22.22.22.22     42          0x80000004 0x00A975
192.168.34.0    11.11.11.11     1808        0x80000005 0x0099A6
192.168.56.0    22.22.22.22     42          0x80000004 0x005DA1
 Observation:

a. Its not relevant to Auckland and Singapore router Anymore as both routers were already members of Area 0 together with Perth and Sydney as we can see from the  Router Link States (Area 0) above. Routers within the same OSPF domain are not expecting to see advertise network of other routers on the same OSPF domain or area. Does this make sense?

b. So here is the catch, since we have created the Virtual link to joined the Two Discontiguous Area 0 and we were successful in joining them, we have couple of routers now on Area 0 and I’m expecting them to have the same LSDB topology. Let’s extract the LSDB of Sydney and Auckland and try to compare them.

Sydney#show ip ospf database

Link ID         ADV Router      Age         Seq#       Checksum
10.10.10.1      11.11.11.11     1341        0x80000004 0x00CE1F
10.10.10.1      22.22.22.22     841   (DNA) 0x80000003 0x00087A
20.20.20.1      11.11.11.11     1341        0x80000004 0x00E7A7
20.20.20.1      22.22.22.22     841   (DNA) 0x80000003 0x001C88
192.168.12.0    11.11.11.11     1341        0x80000004 0x0084D3
192.168.12.0    22.22.22.22     841   (DNA) 0x80000003 0x003BF1
Sydney#

Auckland#show ip ospf database

Link ID         ADV Router      Age         Seq#       Checksum
10.10.10.1      11.11.11.11     1112  (DNA)    0x80000003 0x00D01E
10.10.10.1      22.22.22.22     1240        0x80000004 0x00067B
20.20.20.1      11.11.11.11     1112  (DNA) 0x80000003 0x00E9A6
20.20.20.1      22.22.22.22     1240        0x80000004 0x001A89
192.168.12.0    11.11.11.11     1112  (DNA) 0x80000003 0x0086D2
192.168.12.0    22.22.22.22     1240        0x80000004 0x0039F2
Auckland#

Observation:
 
a. Both router’s LSDB are the same. We can simply check that with the Sequence Number of each LINK ID. In this case the Link ID of 20.20.20.1 has a sequence number of  0x80000004 on both Auckland and Sydney routers.

 7. Finally, I have to check the connectivity between Auckland towards Sydney, Perth and Manila routers.


Auckland to Sydney

Auckland#ping 40.40.40.1 source 60.60.60.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 40.40.40.1, timeout is 2 seconds:
Packet sent with a source address of 60.60.60.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 412/611/708 ms

Auckland to Perth


Auckland#ping 30.30.30.1 source 60.60.60.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 30.30.30.1, timeout is 2 seconds:
Packet sent with a source address of 60.60.60.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 432/541/616 ms

Auckland to Melbourne

Auckland#ping 20.20.20.1 source 60.60.60.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 20.20.20.1, timeout is 2 seconds:
Packet sent with a source address of 60.60.60.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 368/406/452 ms

Auckland to Manila

Auckland#ping 10.10.10.1 source 60.60.60.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.10.1, timeout is 2 seconds:
Packet sent with a source address of 60.60.60.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 416/508/600 ms

Auckland to Singapore
Auckland#ping 50.50.50.1 source 60.60.60.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 50.50.50.1, timeout is 2 seconds:
Packet sent with a source address of 60.60.60.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 108/190/232 ms

This end my laboratory for the second scenarios where we can used OSPF Virtual-links. So my overall assessment as follows:

1. Router-ID is not required to advertise into OSPF. I did this on my first laboratory about Virtual-Link.

2. Used the following command to enable virtual link ” area