Volume 1 - Chapter 22: Implementing Basic OSPF Features

Question 1

What is the command to enter OSPF configuration mode for a particular OSPF process?

Answer 1

router ospf processID

Question 2

What is the command to set a router-ID for an OSPF process?

Answer 2

router-id routerID

Question 3

Assuming a RID has not been manually set, what is the order that the router will use to choose its router-ID dynamically?

Answer 3

The router will choose the highest working loopback.

If no loopback is configure/working, then the highest IP address of any non-loopback interface.

Question 4

What is the command to enable OSPF for a specific network, rather than on a per-interface basis?

Answer 4

network x.x.x.x wildcardmask area areaID

Question 5

What is the range of values for the OSPF router-ID?

Answer 5

Any integer between 1 to 65,535.

Question 6

What are the range of values for the OSPF area ID?

Answer 6

The area can be configured as an integer or dotted decimal format in the range of 0 to 4,294,967,295.

Question 7

A technician enters the following network into the OSPF configuration:

network 172.16.3.2 0.0.255.255 area 0

How with the router interpret this command?

Answer 7

The subnet has been configured incorrectly and does not match the wildcard mask. However, IOS will perform the math to calculate the subnet ID and enter that into the running configuration as:

network 172.16.0.0 0.0.0.255 area 0

Question 8

What are the commands to show the configuration commands of OSPF?

Answer 8

show running-config
show ip protocols

Question 9

What are the commands to show the status of OSPF-enabled interfaces?

Answer 9

show ip ospf interface
show ip ospf interface type number
show ip ospf interface brief

Question 10

What are the commands to show the status of OSPF neighbors?

Answer 10

show ip ospf neighbor
show ip ospf neighbor type number

Question 11

What is the command to display the current LSDB?

Answer 11

show ip ospf database

Question 12

What is the command to display the current RIB?

Answer 12

show ip ospf rib

Question 13

A technician runs the command show ip ospf neighbor and sees the following state for one of its neighbors:

FULL/DR

What does this tell us about the neighbor?

Answer 13

The router has reached a full state and exchanged the LSDB with its neighbor.

The neighboring router is a designated router.

Question 14

A technician runs the command show ip ospf neighbor and sees the following state for one of its neighbors:

FULL/BDR

What does this tell us about the neighbor?

Answer 14

The router has reached a full state and exchanged the LSDB with its neighbor.

The neighboring router is a backup designated router.

Question 15

A technician runs the command show ip ospf neighbor and sees the following state for one of its neighbors:

FULL/DROTHER

What does this tell us about the router the technician is currently connected to?

Answer 15

The technician is currently logged into either the DR, or BDR.

This router has reached a full state and exchanged the LSDB with its neighbor.

Question 16

A technician runs the command show ip ospf neighbor and sees the following state for one of its neighbors:

2WAY/DROTHER

What does this tell us about the neighbor and the router the technician is logged into?

Answer 16

Neither router is a DR or BDR. As such, the routers cannot reach a full state and will not exchange their LSDBs with each other.

Question 17

What state does an interface need to be in to be considered for the OSPF RID?

Answer 17

At least up/down

Question 18

When does a router choose its RID?

Answer 18

When the router first initializes at startup.

Question 19

What options are available to update a routers RID?

Answer 19

Reload the router

Or

Enter the command: clear ip ospf process

Question 20

What is the command to enable OSPF on an interface using an interface rather than network command?

Answer 20

interface interfacename
ip ospf processID area areanumber

For example:

interface Gi0/0/1
ip ospf 1 area 0