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Exam 350-401 topic 1 question 773 discussion

Actual exam question from Cisco's 350-401

Question #: 773
Topic #: 1

SIMULATION
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Guidelines
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This is a lab item in which tasks will be performed on virtual devices.

• Refer to the Tasks tab to view the tasks for this lab item.
• Refer to the Topology tab to access the device console(s) and perform the tasks.
• Console access is available for all required devices by clicking the device icon or using the tab(s) above the console window.
• All necessary preconfigurations have been applied.
• Do not change the enable password or hostname for any device.
• Save your configurations to NVRAM before moving to the next item.
• Click Next at the bottom of the screen to submit this lab and move to the next question
• When Next is clicked, the lab closes and cannot be reopened.

Topology
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Tasks
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Configure OSPF on all three routers according to the topology to achieve these goals:

1. Configure OSPF without using the “network” statement under the “router ospf” configuration section.
2. Ensure that all networks are advertised between the routers.
3. Configure a single command under each Ethernet interface to prevent OSPF neighbors from participating in a DR/BDR election and ensure that no extra host routes are generated.

Show Suggested Answer

Suggested Answer:

by NewLife77 at Aug. 15, 2023, 7:34 p.m.

Comments

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NewLife77

Highly Voted 1 year, 10 months ago

I don't believe the lo0 need ip ospf network point-to-point. It works correctly without it. If someone else believes the loopbacks need it, please let us know. Only the interfaces between the routers need the ip ospf network point-to-point command.

upvoted 13 times

Rfvaz

9 months, 1 week ago

By default the loopback interfaces are advertised by /32, if the question ask to be advertised by /24, so we have to configure the "ip ospf network poin-to-point"

upvoted 3 times

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NavidO

Highly Voted 1 year, 9 months ago

R1 Interface loopback0 Ip address 1.1.1.1 255.255.255.255 Ip ospf 1 area 0 Interface e0/0 Ip address 10.0.0.1 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point R2 Interface e0/0 Ip address 10.0.0.2 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point Interface e0/1 Ip address 192.168.0.2 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point R3 Interface e0/1 Ip address 192.168.0.3 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point

upvoted 7 times

NavidO

1 year, 9 months ago

R2 Interface loopback0 Ip address 2.2.2.2 255.255.255.255 Ip ospf 1 area 0 R3 Interface loopback0 Ip address 3.3.3.3 255.255.255.255 Ip ospf 1 area 0

upvoted 7 times

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Niles_2

Most Recent 2 months ago

In order to fulfill task 3, the subnet mask of the loopback interface has to be /24. If it's configured as /32, it will always be advertised as /32 — at least based on my lab tests. R1 Interface loopback0 Ip address 1.1.1.1 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point Interface e0/0 Ip address 10.0.0.1 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point end wr R2 Interface loopback0 Ip address 2.2.2.2 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point Interface e0/0 Ip address 10.0.0.2 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point Interface e0/1 Ip address 192.168.0.2 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point end wr R3 Interface loopback0 Ip address 3.3.3.3 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point Interface e0/1 Ip address 192.168.0.3 255.255.255.0 Ip ospf 1 area 0 Ip ospf network-type point-to-point end wr

upvoted 1 times

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Rfvaz

9 months, 1 week ago

Guys, Read the question: "under each Ethernet", the question is specifying Ethernet not Loopback.

upvoted 4 times

Kdom07

8 months, 1 week ago

under "ethernet" is only referencing the point-to-point command. in the example here that command is not under the Loop back

upvoted 1 times

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IgorLVG

1 year, 2 months ago

the ans for the last part is ip ospf net point-to-point. i used the priority and the status of DR/BRD still shows in the neighbors; whe i used point-to-point only shows FULL state: Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 0 FULL/ - 00:00:39 192.168.0.2 GigabitEthernet0/0/1

upvoted 1 times

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janbaz

1 year, 3 months ago

In terms of ospf, to configure each Ethernet interface to prevent OSPF neighbors from participating in a DR/BDR election and ensure that no extra host routes are generated, do we use ip ospf network point-to-point or ip ospf priority 0? To prevent OSPF neighbors from participating in a DR/BDR (Designated Router/Backup Designated Router) election and ensure that no extra host routes are generated, you would typically configure the Ethernet interfaces with the ip ospf network point-to-point command. On the other hand, setting the OSPF priority to 0 (ip ospf priority 0) on an interface would effectively prevent that router from becoming a DR or BDR. However, this alone doesn't necessarily prevent the interface from participating in the election process, as it still relies on other routers' priorities to determine the DR and BDR. So, for the scenario you described, ip ospf network point-to-point is the more appropriate configuration command to ensure the desired behavior.

upvoted 2 times

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Tadese

1 year, 5 months ago

Route be Network Type BROADCAST,

upvoted 2 times

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Tadese

1 year, 5 months ago

Let first understand the question. we request to prevent to participated DR/BDR election means there is chance to be DR/BDR but we have to prevent from participation as well as no new extra route shouldn't be generated that means point-to-point route it couldn't be so I seem the answer is #R1 Interface e0/0 ip ospf 1 area 0 ip ospf priority 0 interface lo0 ip ospf 1 area 0 do wr mem #R2 Interface e0/0 ip ospf 1 area 0 ip ospf priority 0 Interface e0/1 ip ospf 1 area 0 ip ospf priority 0 interface lo0 ip ospf 1 area 0 do wr mem #R3 Interface e0/1 ip ospf 1 area 0 ip ospf priority 0 interface lo0 ip ospf 1 area 0 do wr mem

upvoted 3 times

RainHua

4 months, 3 weeks ago

A priority of 0 means the router will never be elected as DR or BDR. Does it means it doesn't participate DR/BDR election? I think even if the priority is set to 0, the router still participates the election process.

upvoted 1 times

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Tadese

1 year, 5 months ago

#R1 Interface e0/0 ip ospf 1 area 0 ip ospf priority 0 interface lo0 ip ospf 1 area 0 do wr mem #R2 Interface e0/0 ip ospf 1 area 0 ip ospf priority 0 Interface e0/1 ip ospf 1 area 0 ip ospf priority 0 interface lo0 ip ospf 1 area 0 do wr mem #R3 Interface e0/1 ip ospf 1 area 0 ip ospf priority 0 interface lo0 ip ospf 1 area 0 do wr mem

upvoted 2 times

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[Removed]

1 year, 9 months ago

also for the part where no extra routes shouldn't be generated: on every router under ospf process: passive-interface default no passive-interface loopback0 no passive-interface e0/0 no passive-interface e0/1 -> on R2 only also, no need for point-to-point network type under loopback interfaces considering /32 subnet.. cant go more than that :)

upvoted 2 times

mgiuseppe86

1 year, 9 months ago

Negative.. I think you are wrong. Step 3 asks for a single command, that is network-type point-to-point passive-interface default and then having to do 'no passive-interface" is 2 commands and more. Again, Step 3 asks for a SINGLE COMMAND to accomplish TWO tasks.

upvoted 3 times

Alondrix

1 year, 7 months ago

Passive interface applied to e0/0 and e0/1 would break the neighbor adjacency and stop ospf routing. It could be used on Lo0, but that isn't what is needed. To prevent the BR/BDR election it would be on the interface, "ip ospfy network-type point-to-point".

upvoted 2 times

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eddgg

1 year, 9 months ago

If we create a loopback and give classful or classless addresses, then by default the route to that loop back is advertised as the most specific route: /32 prefix and it will ignore any configured prefix. Eg: interface Loopback0 ip address 2.2.2.2 255.255.255.0 Here, the loopback network address is 2.2.2.0/24. By default OSPF will advertise this route to loopback0 as 2.2.2.2/32 (most specific route to that loopback). To override this we have to change the network type to point-to-point. After this OSPF will advertise the address to loopback as 2.2.2.0/24. interface Loopback0 ip address 2.2.2.2 255.255.255.0 ip ospf network point-to-point

upvoted 1 times

NewLife77

1 year, 9 months ago

Out of curiosity, why would we want to change it to 2.2.2.0/24? Why not keep it as 2.2.2.2/32? The question is showing its already configured as 2.2.2.2/32. Your example here is showing it as 2.2.2.2/24. Please clarify.

upvoted 1 times

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