Cisco CCNA Certification Exam Tutorial: The OSPF RID

OSPF is a major topic on your CCNA exam, as well it should be. OSPF is a widely-used WAN protocol, and you need to learn the fundamentals before moving on to more complicated configurations. One such detail is the OSPF Router ID, or RID.

The RID is the dotted decimal value by which other OSPF routers will identify a given OSPF router. There are some interesting defaults for this value, and a command you should know to hardcode the RID. You had also better know what has to happen for this command to take effect, so let’s take a more detailed look at the OSPF RID.

In this example, R1 has an adjacency with R2 and R3 over the frame network. R1 is the hub, with R2 and R3 as the spokes. No other interfaces are OSPF-enabled on any of the routers. Running show ip ospf neighbor on R1, we see some unusual values under “Neighbor ID”, which is another name for the OSPF RID.

R1#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface 0 FULL/DROTHER 00:01:57 Serial0 0 FULL/DROTHER 00:01:57 Serial0

Notice the Neighbor ID of each remote address is the loopback address. How can that be if they’re not OSPF-enabled?

When determining the Router ID (RID) of an OSPF-enabled router, OSPF will always use the numerically highest IP address on the router’s loopback interfaces, regardless of whether that loopback is OSPF-enabled.

What if there is no loopback? OSPF will then use the numerically highest IP address of the physical interfaces, regardless of whether that interface is OSPF-enabled.

BOTTOM LINE: An interface does not have to be running OSPF to have its IP address used as the OSPF RID.

The OSPF RID can be changed, but it requires a restart or to reinitialize the OSPF routing process. Use the router-id command to change the default RID of each router as shown, and clear the OSPF process to do so.

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#router ospf 1


Reload or use “clear ip ospf process” command, for this to take effect

R1#clear ip ospf process

Reset ALL OSPF processes? [no]: yes

1d05h: %OSPF-5-ADJCHG: Process 1, Nbr on Serial0 from 2WAY to
DOWN, Neighbor Down: Interface down or detached

1d05h: %OSPF-5-ADJCHG: Process 1, Nbr on Serial0 from 2WAY to
DOWN, Neighbor Down: Interface down or detached

After entering the router-id command, the router console informed you that you have to reload the router or reset the OSPF processes for this to take effect. You enter the clear ip ospf process command to do this. Notice that when you’re asked if you really want to do this, the prompt is “no”? That’s because all the OSPF adjacencies on this router will be lost and will have to begin the process again. That’s OK on a practice rack, not good in a production network. Don’t use that one at work.

The OSPF RID is not a complicated concept, but the fact that an interface doesn’t have to be OSPF-enabled in order to have its IP address act as the RID takes some getting used to. And remember – when the router or switch asks you a question and the prompted answer is “no”, take one step back and make sure you really want to do what you’re about to do!

Exam 70-270 – Microsoft’s MCDST Windows XP Examination Guidelines

Exam 70-270 is one of the Microsoft certification examinations and the name of the examination is MCDST Windows XP. This certification is designed for the candidates who wish to gain knowledge and skills in the ability to solve the end user incident request by troubleshooting as well as configuring windows XP operating system. This examination is one of the examinations for certifying MCDST certification. Exam 70-271 is the other examination for certifying with MCDST.

Prerequisites for this examination:

For writing this exam, there are no specific prerequisites required for the candidates but it is recommended to have some basic knowledge about the Windows XP operating system like Windows XP home edition, XP professionals that include with Microsoft office tools as well as Microsoft outlook express.

How to practice for the exam?

Candidates can practice for this exam by reading the following sections and they are:

1) Installation process of windows XP professionals on your computer
2) Configuration of internet connection firewall components (ICF)
3) Configuration as well as testing several TCP/ IP by using commands such as PATCHPING, PING and TRACERT.

Exam objectives:

The following are the examination objectives of 70-270 and they are:

1) Configuring application security
2) Solving issues that is related with usability
3) Troubleshooting as well as configuring applications
4) Solving issues related with customizing applications
5) Troubleshooting as well as configuration connectivity for the applications.

Job roles and other details of the exam:

After successful completion of this examination, candidates can get several job opportunities for several positions in the top companies. Some of the job roles include: PC support specialists, technical support specialists, customer support representatives etc. The exam comprises of 50 multiple choices, drag-drop, built a tree, reorder type questions. Time duration is approximately 90 minutes and the minimum score to pass in this examination is 700 out of 1000 (70%).