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OSPF Sim

January 8th, 2019 in Lab Sim, LabSim Go to comments

Question

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.

OSPFSim

Your task is to configure the following:

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).

Answer and Explanation:

First, we configure Portland’s S0/0 interface so that it belongs to Area 1. So, we have to find out which sub-network the IP address 192.168.4.5/30 (the IP of interface S0/0 of Portland) belongs to. This address belongs to a subnetwork which has:

Increment: 4 (/30 = 255.255.255.252 or 1111 1111.1111 1111.1111 1111.1111 1100)
Network address: 192.168.4.4 (because 4 = 4 * 1 and 4 < 5)
Broadcast address: 192.168.4.7 (because 7 = 4 + 4 – 1) (It is not necessary to find out the broadcast address but we should know it)

The question requires that only Portland’s S0/0 and Amani’s S0/1 could be in Area 1, therefore we must use a wildcard of 0.0.0.3 (this wildcard is equivalent with a subnet mask of /30) so that there are only 2 IP addresses can participate in area 1 (they are 192.168.4.5 & 192.168.4.6). The full command we use here is network 192.168.4.4 0.0.0.3 area 1

The question also requires that “Area 1 should not receive any external or inter-area routes (except the default route)”. Recall that if we don’t want the router to receive external routes, we have to stop LSA Type 5. And if we don’t want to receive inter-area routes, we have to stop LSA Type 3 and Type 4. Therefore we have to configure area 1 as a totally stubby area. For your information, here is the definition of a totally stubby area:

Totally stubb area – This area does not accept summary LSAs from other areas (types 3 or 4) or external summary LSAs (Type 5). Types 3,4 and 5 LSAs are replaced by the Area Border Router(ABR) with a default router. Totally stubby areas protect internal routers by minimizing the routing table and summarizing everything outside the area with a default route.” (CCNP BSCI Official Exam Certification Guide, Fourth Edition)

In conclusion, we have to configure area 1 as a totally stubby area. We do that by configuring Portland as stub and configuring Amani (ABR router) as a stub + “no-summary”suffix.

+ Configure Portland router as a stub:

Portland#configure terminal
Portland(config)#router ospf 1

Allow network 192.168.4.4/30 to join Area 1, notice that you have to convert subnet mask into wildcard mask:

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

Configure Portland as a stub:

Portland(config-router)#area 1 stub

Portland(config-router)#end
Portland#copy running-config startup-config

+ Configure Amani router as a “totally stub”:

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

Make area 1 become a totally stubby area, notice that we can only use this command on ABR router:

Amani(config-router)#area 1 stub no-summary

Amani(config-router)#end
Amani#copy running-config startup-config

Note: Make sure to check the OSPF process ID before typing your configuration. Maybe it is not OSPF process 1 like the configuration above.

 

Other lab-sims on this site:

EIGRP Stub Sim

EIGRP OSPF Redistribution Sim

IPv6 OSPF Virtual Link Sim

EIGRP Simlet
Policy Based Routing Sim

 

Comments
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  1. Mantas
    November 30th, 2019

    as it specifically asks to use network command with ‘appropriate mask’ would it be wrong to use interface configuration command ‘ ip ospf 1 area 1’ instead?

  2. Jiffy
    December 8th, 2019

    I saw a study guide using “network 192.168.4.5 0.0.0.0 area 1” as a more specific mask. Is this right?

  3. asna
    December 10th, 2019

    dumps are valid??? did anyone make an attempt recently

  4. LarryGaGa
    December 14th, 2019

    Any one with the latest SWITCH dumps 300-115, send to me and i will reply with the latest ROUTE 300-101. I just passed with 864, email me for confirmation. owenizevbokun(at)gmail(dot)com

  5. Switch
    January 2nd, 2020

    @digitalhut et All
    For this sim I want to make sure I have this right. Configure R1(Portland) and R2(Amani), can’t config R3(Lynaic) in the exam. R1 and R2 should be as is in the answers above. Questions are in the exam will the interfaces already be configured and on R2(Amani) will Area 0 already be configured. When I check OSPF neighbors and ip route should I only see the adjacent neighbor for each and only directly connected routes under ip route check. I can ping from Lynaic to Portland S0/0. This lists no checks so need to make sure what we should be seeing when checking those so we know all is correct in the lab before moving on. From my GNS3 lab setup for this.
    Portland#show ip ospf neighbor

    Neighbor ID Pri State Dead Time Address Interface
    192.168.72.6 0 FULL/ – 00:00:32 192.168.4.6 Serial0/0
    Portland#show ip route
    Gateway of last resort is 192.168.4.6 to network 0.0.0.0
    192.168.4.0/30 is subnetted, 1 subnets
    C 192.168.4.4 is directly connected, Serial0/0
    O*IA 0.0.0.0/0 [110/65] via 192.168.4.6, 00:00:31, Serial0/0

    Anami#show ip ospf neighbor

    Neighbor ID Pri State Dead Time Address Interface
    223.239.239.239 0 FULL/ – 00:00:37 192.168.72.5 Serial0/0
    192.168.4.5 0 FULL/ – 00:00:38 192.168.4.5 Serial0/1
    Anami#show ip route
    Gateway of last resort is not set
    192.168.72.0/30 is subnetted, 1 subnets
    C 192.168.72.4 is directly connected, Serial0/0
    223.239.239.0/32 is subnetted, 1 subnets
    O IA 223.239.239.239 [110/65] via 192.168.72.5, 00:02:12, Serial0/0
    192.168.4.0/30 is subnetted, 1 subnets
    C 192.168.4.4 is directly connected, Serial0/1

    Lynaic#sh ip ospf neighbor

    Neighbor ID Pri State Dead Time Address Interface
    192.168.72.6 0 FULL/ – 00:00:31 192.168.72.6 Serial0/1
    Lynaic#show ip route
    Gateway of last resort is not set
    192.168.72.0/30 is subnetted, 1 subnets
    C 192.168.72.4 is directly connected, Serial0/1
    223.239.239.0/32 is subnetted, 1 subnets
    C 223.239.239.239 is directly connected, Loopback0
    192.168.4.0/30 is subnetted, 1 subnets
    O IA 192.168.4.4 [110/128] via 192.168.72.6, 00:03:58, Serial0/1

    Lynaic#ping 192.168.4.5

    Type escape sequence to abort.
    Sending 5, 100-byte ICMP Echos to 192.168.4.5, timeout is 2 seconds:
    !!!!!
    Success rate is 100 percent (5/5)

  6. Burns
    January 5th, 2020

    should the command not include network 192.168.4.72.4 area 0 on armani also?

    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
    Amani(config-router)#network 192.168.4.72.4 area 0

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