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Question 747

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 diagram to achieve these goals:

1. Enable OSPF on all interfaces using the network statement and match the network mask of each interface.

2. Ensure that all networks are advertised between the routers.

3. Ensure that all routers use OSPF process ID 1 and that the Lo0 interface is used for the router ID.

4. Configure OSPF MD5 authentication on every physical interface running OSPF using key 1 and the password ccnp321.

    Correct Answer:

Discussion
asiansensation

R1 interface Loopback0 ip address 1.1.1.1 255.255.255.255 interface Ethernet0/0 ip address 10.0.0.1 255.255.255.0 ip ospf authentication message-digest ip ospf message-digest-key 1 md5 ccnp321 router ospf 1 router-id 1.1.1.1 network 1.1.1.1 0.0.0.0 area 1 network 10.0.0.0 0.0.0.255 area 0 R2 interface Loopback0 ip address 2.2.2.2 255.255.255.255 interface Ethernet0/0 ip address 10.0.0.2 255.255.255.0 ip ospf authentication message-digest ip ospf message-digest-key 1 md5 ccnp321 interface Ethernet0/1 ip address 192.168.0.2 255.255.255.0 ip ospf authentication message-digest ip ospf message-digest-key 1 md5 ccnp321 router ospf 1 router-id 2.2.2.2 network 2.2.2.2 0.0.0.0 area 0 network 10.0.0.0 0.0.0.255 area 0 network 192.168.0.0 0.0.0.255 area 0 R3 interface Loopback0 ip address 3.3.3.3 255.255.255.255 interface Ethernet0/1 ip address 192.168.0.3 255.255.255.0 ip ospf authentication message-digest ip ospf message-digest-key 1 md5 ccnp321 router ospf 1 router-id 3.3.3.3 network 3.3.3.3 0.0.0.0 area 3 network 192.168.0.0 0.0.0.255 area 0

Cryptoking112211

Router 3 is in Area 2 - not area 3 ..... R3 interface Loopback0 ip address 3.3.3.3 255.255.255.255 interface Ethernet0/1 ip address 192.168.0.3 255.255.255.0 ip ospf authentication message-digest ip ospf message-digest-key 1 md5 ccnp321 router ospf 1 router-id 3.3.3.3 network 3.3.3.3 0.0.0.0 area 2 network 192.168.0.0 0.0.0.255 area 0

tempaccount00001

I would agree with this! usually interfaces are configured already, if not then verify with "show ip interface brief". if the interfaces aren't configured, they are most likely also shut down, so make sure you dont get caught on the "no shut". verify with "show ip ospf neighbor". This would be my config BTW, almost exactly like yours: R1: router ospf 1 id 1.1.1.1 network 1.1.1.1 0.0.0.0 network 10.0.0.0 0.0.0.255 int e0/0 ip ospf authentication message-digest ip ospf message-digest-key 1 MD5 ccnp321 R2: router ospf 1 id 2.2.2.2 network 2.2.2.2 0.0.0.0 network 10.0.0.0 0.0.0.255 network 192.168.0.0 0.0.0.255 int e0/0 ip ospf authentication message-digest ip ospf message-digest-key 1 MD5 ccnp321 int e0/1 ip ospf authentication message-digest ip ospf message-digest-key 1 MD5 ccnp321 R3: router ospf 1 id 3.3.3.3 network 3.3.3.3 0.0.0.0 network 192.168.0.0 0.0.0.255 int e0/1 ip ospf authentication message-digest ip ospf message-digest-key 1 MD5 ccnp321

sledgey121

Area 0 is within the solid lines, area 1 and 2 are within the dashed lines. The whole of R2 is area0 and only the R1/R2 loopbacks are the different areas. Only configure the auth on the interfaces.

a197cbf

I agree, I interpreted the 10.0.0.0/24 and 192.168.0.0/24 networks both as part of area 0, and only R1 and R3's loopbacks were in their own respective areas.

VincentY

Two mistakes here. 1. The area configurations are wrong. Notice the types of the line in the exhibit. 2.The

VincentY

2. The “authentication on every physical interface” indicates the authentication command should all be on the physical interfaces.

HungarianDish

authentication: task: "Configure OSPF MD5 authentication on every physical interface running OSPF" -> I assume that they requested a configuration per interface, and NOT per area: interface e0/0 ip ospf message-digest-key 1 md5 ccnp321 ip ospf authentication message-digest https://networklessons.com/ospf/how-to-configure-ospf-md5-authentication You can enable "authentication message-digest" under the ospf process for an entire area. or You can enable it under the interface.

[Removed]

I would configure the authentication on the interfaces instead of the router ospf process

Symirnian

R1# router ospf 1 #router-id 1.1.1.1 #network 1.1.1.1 0.0.0.0 area 1 #network 10.0.0.0 0.0.0.255 area 0 #exit #interface e0/0 #ip ospf message-digest-key 1 md5 ccnp321 #ip ospf authentication message-digest #do write R2#router ospf 1 #network 2.2.2.2 0.0.0.0 area 0 #network 10.0.0.0 0.0.0.255 area 0 #network 192.168.0.0 0.0.0.255 area 0 #interface range e0/0-1 #ip ospf message-digest-key 1 md5 ccnp321 #ip ospf authentication message-digest #do write

HungarianDish

router-ID: - we do not need to specify the router-id explicitly, because the ip of loopback0 was elected as the router-id automatically OSPF uses the following criteria to select the router ID: Manual configuration of the router ID. Highest IP address on a loopback interface. Highest IP address on a non-loopback interface. https://networklessons.com/ospf/ospf-router-id

Steve122

It is recommended to conf. the router-id explicitly.

Symirnian

I think answer is wrong! 3 routers should have "area 0" command. All interfaces of R2 should be in area 0 and the counter interface on R1 and R3 must be in area 0 too. What is your opinion?

Badger_27

I think you are right.

Nickplayany

Hey! I think you are wrong. Read more about it and check the exact same scenario here:https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/xe-16/iro-xe-16-book/iro-cfg.html Search for Example: Complex Internal Router with ABR and ASBR

Symirnian

On the design area0 is continued line and ABR is R1 and R3. area 2 and area 1 are dashed lines on R1 and R3 other sides.

HungarianDish

The area configuration of the provided solution is correct. However, I am not sure that the router-ID and the authentication are configured as specified in the task.

danman32

Makes you wonder if exam expects you to statically set the router ID to "ensure" the desired router ID, or let auto determination of router ID which would use the L0 interface as ID. Could be the test grades on whether the RID matches the L0 IP, regardless of your method. I agree with others, all physical segments are within area 0 based on the dashed lines. But probably the biggest scoring is the wildcard masks used for the network statements, and that you configured a working MD5 authentication.

HungarianDish

I tested the two possible configs in CML. It works both way. 1) R1 and R3 can also have their physical interface in "area 0" -> so, R1 and R3 become ABR for non-backbone areas 2) however, it is enough to place only the loopback of R2 in "area 0", and all the rest can be in non-backbone areas -> R2 becomes ABR It depends on the desired design. Some sources: https://notes.networklessons.com/ospf-backbone-area-0 All non-backbone areas must have an ABR that is also connected to Area 0. ... Area 0 must exist on at least one interface of an ABR router. https://lpmazariegos.com/2016/02/02/interconnecting-ospf-areas/ Backbone Router – Routers where at least one OSPF interface must belong to area 0 (backbone area).