Module-13 Chapter 2: Single-Area OSPFv2 Configuration

What command enables OSPFv2 globally?

router ospf [process-id]

What is the process ID in OSPFv2 configuration?

A locally significant identifier for the OSPF process (can be any number).

What command assigns a router ID manually?

router-id [router-id]

What is a router ID in OSPF?

A unique 32-bit value used to identify a router in OSPF.

How is the router ID chosen if not configured manually?

Highest IP address on an active interface, or highest loopback IP if present.

How can you force the router to recalculate the router ID?

Clear the OSPF process using clear ip ospf process.

What command advertises a network in OSPFv2?

network [network-address] [wildcard-mask] area [area-id]

What does the wildcard mask do in OSPF?

It determines which interface(s) the network command applies to.

What does 0.0.0.0 wildcard mask mean?

Match the exact interface IP address.

What command shows all interfaces participating in OSPF?

show ip ospf interface brief

What command shows OSPF neighbors?

show ip ospf neighbor

What command shows OSPF database info?

show ip ospf database

What command shows OSPF routing table entries?

show ip route ospf

What command shows OSPF process ID and router ID?

show ip protocols

What does OSPF use to form neighbor relationships?

Hello packets.

What must match for routers to form OSPF adjacencies?

Hello/dead intervals, area ID, subnet, authentication, and stub flag.

What are the default hello and dead intervals?

10 seconds (hello), 40 seconds (dead).

What is the command to set hello and dead intervals?

ip ospf hello-interval [seconds] and ip ospf dead-interval [seconds]

What command enables OSPFv2 on an interface (alternative to network)?

ip ospf [process-id] area [area-id]

Why might you use interface-level OSPF configuration?

For more control or when using point-to-point interfaces.

How can OSPF neighbors be verified?

Using show ip ospf neighbor command.

What is the DR/BDR election based on?

Router priority, or highest router ID if tied.

What command sets router priority?

ip ospf priority [value]

What priority value prevents a router from becoming DR/BDR?

0

Where is DR/BDR election relevant?

Only on broadcast multiaccess networks like Ethernet.

Does point-to-point link use DR/BDR?

No, point-to-point does not elect DR/BDR.

How do you reset OSPF neighbor relationships?

clear ip ospf process

What is passive-interface default?

Prevents OSPF from sending Hello packets on all interfaces by default.

How do you enable OSPF on specific interfaces only?

Use passive-interface default, then use no passive-interface [interface-name].

What command displays OSPF interface timers and area?

show ip ospf interface [interface]

What command verifies if an interface is OSPF-enabled?

show ip protocols or show ip ospf interface brief

What is the default OSPF administrative distance?

110

Can OSPF support multiple areas?

Yes, but in this module we focus on single-area OSPF.

What command assigns a router to area 0?

network [address] [wildcard-mask] area 0

Why is area 0 special in OSPF?

It is the backbone area; all other areas must connect to it.

What happens when you configure a new OSPF process?

A new OSPF instance is created with its own database.

How do you view OSPF LSDB?

show ip ospf database

What is the effect of multiple interfaces in the same area?

All their routes are shared and visible in the OSPF LSDB.

How does OSPF calculate route cost?

Based on the bandwidth of the interface (default formula: 100,000,000/bandwidth in bps).

What command changes interface cost manually?

ip ospf cost [value]

What is the purpose of modifying OSPF cost?

To influence path selection.

What is the effect of changing the OSPF cost on an interface?

It can influence which path is preferred when multiple OSPF paths exist.

What is the purpose of the command 'show running-config | section ospf'?

It displays the OSPF-related portion of the active configuration.