CCNA 200 301 Questions // Question 044

The Correct Answer: 1, 2 and 4
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Correct Methods to Activate OSPF Advertisements:
2. Area Assignment Through Network Declarations
• This is the traditional and most common method of enabling OSPF on Cisco routers.
• Under the OSPF process (router ospf process-id), you use the network command to specify:
o Which interfaces should run OSPF (using an IP address and wildcard mask).
o Which OSPF area those interfaces belong to.
4. Interface-Level OSPF Activation Using ip ospf Commands
• Instead of using the network command under the OSPF process, you can enable OSPF directly on an interface with:
o interface GigabitEthernet0/0
o ip ospf 1 area 0
• Advantages:
o More precise control (no need for wildcard masks).
o Useful when only specific interfaces should run OSPF.
• Disadvantages:
o Less scalable (must be configured per interface).
o Not supported on all Cisco platforms (older IOS versions may not allow this).
•

Why the Other Options Are Incorrect:
1. Global Network Statement with Wildcard Mask (Incomplete)
• While this is part of OSPF configuration, just specifying a network with a wildcard mask is not enough—you must also assign an area (which is covered in Option 2).
• Example of an incomplete (and thus incorrect) configuration:
o router ospf 1
o network 10.0.0.0 0.255.255.255 # Missing area assignment!
3. Static Default Route Redistribution (Unrelated to Adjacency Formation)
• Redistribution injects external routes (like static or RIP routes) into OSPF, but it does not enable OSPF on interfaces or form adjacencies.
5. Passive-Interface Configuration (Prevents Adjacency Formation)
• The passive-interface command stops OSPF Hello packets on an interface, preventing adjacency formation.
 

OSPF Adjacency Formation Process:
1. Hello Packet Exchange (Multicast 224.0.0.5)
o Must match on:
 Area ID
 Authentication
 Hello/Dead intervals
 MTU
 Network type
2. Database Synchronization
o DBD packets exchange LSAs
o LSR/LSU packets complete synchronization
3. Full Adjacency
o Routes advertised via LSU packets
o Maintained by regular hello packets
Enterprise Deployment Considerations:
Interface Method Advantages:
• Precise control over which interfaces run OSPF
• Clear visibility in interface configuration
• Easier troubleshooting per interface
Network Statement Advantages:
• Efficient for activating multiple interfaces
• Useful when interfaces share addressing patterns
• Traditional approach familiar to many engineers
Common Mistakes to Avoid:
• Overlapping network statements causing unpredictable activation
• Mismatched area IDs on shared segments
• Forgetting to include backbone area (area 0) in multi-area designs
• Omitting network statements for transit links

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Domain
IP Connectivity

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