OSPF Stub Area Sim configuration on GNS3:

Question
A company has three  routers Protland, Amsni and Lynaic. OSPF is configured on routers Amani and Lynaic. Amani’s S0/0 interface and Lynaic’s S0/1 interface are in Area 0. Lynaic’s Loopback0 interface is in Area 2. Details of configuration are as follow:
Portland’s S1/0 interface in Area 1
Amani’s S1/0 interface in Area 1
Use the appropriate mask such that ONLY Portland’s S0/0 and Amnani’s S0/1 could be in Area 1.
Area 1 should not receive any external or inter-area routes (except the default route).


GNS3 Configurations:
First you need to create this topology in GNS3 as show above with following configurations.
Portland Router:
R1#config t
R1 (config)# hostname Portland
Portland (config)# enable secret cisco
Portland (config)#interface Serial1/0
Portland (config-if)# ip address 192.168.4.5 255.255.255.252
Portland (config-if)#no shutdown
Anami Router:
R2#config t
R2 (config)# hostname Anami
Anami (config)# enable secret cisco
Anami (config)#interface Serial1/0
Anami (config-if)# ip address 192.168.4.6 255.255.255.252
Anami (config-if)# no shutdown
Anami (config)#interface Serial1/1
Anami (config-if)# ip address 192.168.72.6 255.255.255.252
Anami (config-if)#no shutdown
Anami (config)#exit
Anami (config)#router ospf 1
Anami (config-router)# network 192.168.4.4 0.0.0.3 area 1
Anami (config-router)# network 192.168.72.4 0.0.0.3 area 0

Lynaic Router:
R3#config t
R3 (config)# hostname Lynaic
Lynaic (config)# enable secret cisco
Lynaic (config)#interface loopback 1
Lynaic (config-if)# ip address 239.239.239.239 255.255.255.255
Lynaic (config-if)# ex
Lynaic (config)#interface Serial1/0
Lynaic (config-if)# ip address 192.168.72.5 255.255.255.252
Lynaic (config-if)#no shutdown
Lynaic (config)#exit
Lynaic (config)#router ospf 1
Lynaic (config-router)# network 239.239.239.239 0.0.0.0 area 2
Lynaic (config-router)# network 192.168.72.4 0.0.0.3 area 0

Configuratio that you need  in real exam:
From above configuration you have notice that Portland router and Anami’s S1/0 interface is not running OSPF that way they are not able to communicate with other. In order to complete the configuration you need to run OSPF on these. For appropriate mask for 192.168.4.5\30 you need to find out the network ID for this subnet.
1
2
3
4
5
6
7
8
128
64
32
16
8
4
2
0
As we know that \30 is 6th bit of 4th octet that way from above table these subnets are divided into four number differences as follow.





Subet IDs for \30
Broadcast Address
0
3
4
7
8
11
12
15
And so on…….
……..

And from above we can see that 192.168.4.5 lie in 4-7 range therefore
Subnet ID=192.168.4.4

Portland#configure terminal
Portland(config)#router ospf 1
Portland(config-router)#network 192.168.4.4 0.0.0.3 area 1

“Area 1 should not receive any external or inter-area routes” configure area 1 as totally stubby area.

Portland(config-router)#area 1 stub
Portland(config-router)#end
Portland#copy running-config startup-config

Amani#configure terminal
Amani(config)#router ospf 1
Amani(config-router)#network 192.168.4.4 0.0.0.3 area 1
Amani(config-router)#area 1 stub no-summary

Testing:

Ping from Lynaic to Portland should be successful and Lynaic have all route in its routing table.
more CCNP Route Labs

19 comments:

  1. thank you for configuring on gns3.

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  2. "In order to complete the configuration you need to run EIGRP on these."

    I think that use of EIGRP in your sentence is a mistake, I would say OSPF instead, otherwise i don't understand the meaning.

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  3. hmmm i think some thing is missing because i did same as u did but my ping is not responding ...

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    Replies
    1. set interfaces as: no shutdown

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  4. i cannot ping 239.239.239.239 from portland. what is the problem??

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  5. from which router u r try pinging??? n do find the 239.239.239.239 route in routing table??

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  6. 239.239.239.239 shouldn't be a valid host route as it is a multicast address...

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  7. Doesnt matter if its a mulitcast address or not. If its being advertised in the ipv4 routing table and all the routes in the chain have a path to get there then it should be pingable. I tried the lab and it works. Please make sure that loop1 is being advertised into the ospf domain.

    Very simple guys. Good luck.

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    Replies
    1. you can try any other IP address instead of this multicast address, and i think this will works fine.

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  8. how can we check (test our sim is correctly configured or not) this sim after config ?
    i was unable to assign this class D ip address 239.239.239.239.i used 10.239.239.239

    Please advice me.planing to exam next week.
    Thanks for all.

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  9. i cant ping Portland from Lynaic , but the opposite i can.. why ?

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  10. My bad ,PORTLAND will receive a default route automatically,i forgot to configure Anami as stub.Sorry for the spam.

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  11. Question. I used network 192.168.4.6 0.0.0.0 area 1 instead of 0.0.0.3. It actually has the same result but would I lose points on the exam for doing it this way? Thanks.

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    Replies
    1. network 192.168.4.6 0.0.0.0 representing only single IP i.e. "192.168.4.6" because zero in wildcard mask mean "match exactly". whereas 0.0.0.3 mean 192.168.4.6/30 which have two valid IP addresses i.e. 192.168.4.5 & 192.168.4.6..

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  12. hi brothers and sisters..i have question regarding OSPF Sim.how suppose we know the process id?during the exam it will mention that we need to use X process id ?
    from this question :-

    Portland’s S0/0 interface in Area 1
    Amani’s S0/1 interface in Area 1
    Use the appropriate mask such that ONLY Portland’s S0/0 and Amnani’s S0/1 could be in Area 1.
    Area 1 should not receive any external or inter-area routes (except the default route).

    which one is process id?thanks

    ReplyDelete
    Replies
    1. You can easily find the process-id of OSPF that is running on the router by running "sh ip protocol" that will list the dynamic routing processes on the router.

      That's basic dynamic routing knowledge, you should study that before tackling OSPF.

      Delete
  13. Hey Syahir,
    In the real exam they will give you the OSPF process id. And you can even use "show run" to figure it out by yourself. Just make sure you are making the changes under the same process or it won't work. :D

    ReplyDelete
  14. Thanks for the configuration, to those who can't ping ..make sure that u allocate networks to correct area.

    ReplyDelete

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