OSPF Confusion

JBeam

I'm currently enrolled at a Cisco academy for the CCNA, we are finishing up Semester 3 and I took the practice exam today. I got this question wrong and I don't understand the reasoning, can someone help me out?

Router XYZ is to be added to OSPF area 0. Which of the following is the correct syntax for enabling OSPF on this router? 
	XYZ(config)# router ospf 
	XYZ(config)# router ospf 0 
	XYZ(config)# router ospf 10 
	XYZ(config)# router ospf process 0 
	XYZ(config)# router ospf process 10 
	XYZ(config)# router ospf processid 10

The correct answer is option 3. I chose option 2. To assign it to Area 0 wouldn't that be the correct command? I asked my instructor, but his answer just confused me more so I'm lookin for some other views.

Thanks

rossonieri#1

hello,

nope --- you are wrong

pls check your note,

your instructor maybe told you to look again your note

conf#router ospf <proc-id>
conf-router#network <ipsubnet> <inv-mask> area <area>

cheers...

mikej412

The area 0 was just a distraction.

You set the process id on the router ospf command line. You set the area on the network command line.

The question was the correct syntax for "enabling OSPF" -- with is the router ospf command.

Process ID is required and the valid range is 1-65535. Only the 3rd one is the correct syntax for enabling OSPF.

R3640-1#config t
Enter configuration commands, one per line.  End with CNTL/Z.
R3640-1(config)#router ospf ?
  <1-65535>  Process ID

R3640-1(config)#router ospf 1
R3640-1(config-router)#network 10.32.0.0 0.0.255.255 ?
  area  Set the OSPF area ID

R3640-1(config-router)#network 10.32.0.0 0.0.255.255 area ?
  <0-4294967295>  OSPF area ID as a decimal value
  A.B.C.D         OSPF area ID in IP address format

R3640-1(config-router)#network 10.32.0.0 0.0.255.255 area 0

mgeorge

Answer 3 would be correct

Answer 2 would be incorrect because you cannot use Process ID 0. It will give you an error.

Explination;

Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#router ospf ?
<1-65535> Process ID

Router(config)#router ospf

You see you have to select a process id between 1 and 65535.

Answer 1 would be %Incomplete Command.
Answer 2 would be % Invalid input detected at '^' marker.
Answer 3 would be Correct.
Answer 4 would be %Unreconized Command.
Answer 5 would be %Unreconized Command.
Answer 6 would be %Unreconized Command.

To assign a network to a paticular area you use the command
Router(config-router)#network <networkip> <wildcard> area <area>

Example;
Router(config-router)#192.168.0.0 0.0.0.255 area 0

Hope this helps, enjoy

mgeorge

Rrrrrr, looks like mike beat me to it AGIAN!!!

This is starting to become an everyday thing mike lol...

JBeam

I understand now. Thanks for explaining. My instructor just said "0 isnt a proccess id" and that was it =/

JBeam

Another OSPF Question:

What will be the result of OSPF DR/BDR elections in the network shown in the diagram? (Choose three.)
R1 will be the DR for the 10.1.1.0/24 network.
R1 will be the DR for the 10.1.2.0/24 network.
R1 will be the DR for the 10.1.3.0/24 network.
R2 will be the DR for the 10.1.1.0/24 network.
R3 will be the DR for the 10.1.2.0/24 network.
R4 will be the DR for the 10.1.3.0/24 network.

I got this one right, I chose Options 2, 4 and 6. But now that I review, I'm not sure how I came up with the answer. I read the section again and it says that the highest Router ID will be come the DR, and to get the router ID its based off the IP address. Therefore wouldn't 1, 3, and 5 be correct?

JBeam

I figured it out, Its the HIGHEST IP on the router, makes it the default route. Been looking for the reasoning and found it! Thanks

darkuser

here's a nice ospf link ....

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr_c/ipcprt2/1cfospf.htm