Tag Archives: Exam

Cisco CCNA Certification Exam Tutorial: The OSPF RID

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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 172.12.123.0/24 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

3.3.3.3 0 FULL/DROTHER 00:01:57 172.12.123.3 Serial0

2.2.2.2 0 FULL/DROTHER 00:01:57 172.12.123.2 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

R1(config-router)#router-id 11.11.11.11

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 3.3.3.3 on Serial0 from 2WAY to
DOWN, Neighbor Down: Interface down or detached

1d05h: %OSPF-5-ADJCHG: Process 1, Nbr 2.2.2.2 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!

How to Avoid Anxiety Caused By Exams

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The older you get, the more stressful exams may become. As a student, you may be anxious about your exams for various reasons. The fear of letting your parents or teachers down, or failing to succeed, can all add to your nervousness and cause you to have anxiety attacks. Anxiety is not only exhausting; it can also render you incapable of giving your best performance. Hence, if you have an upcoming exam, it is essential for you to not only prepare but also to ensure an anxiety-free exam session. Here’s how to do so.

Eat well: Often, when studying for exams, we forget and sometimes even avoid taking our meals, trying not to waste precious minutes that can be spent studying. This is very harmful for our body, which will continue working on adrenaline for a while, but will eventually give out when we most need it. Anxiety attacks make the blood pressure and blood sugar drop, and this in turn leads to dizziness and nausea. To avoid feeling lethargic and panicking before an exam, keep yourself well-fed and in good shape, as this will do wonders for your confidence and help you remain anxiety-free.

Sleep right: As with the dietary habits, sleeping habits also play a huge part in causing you to have anxiety-related panic attacks. Make sure you are relaxed and have slept well before your exam, for lack of sleep can exhaust you and keep you from being at the top of your game, leading to an anxiety attack. Your study routine should give you a minimum of six hours of sleep, so that you are fresh and alert not only when studying, but also on the day of the exam. Make sure you don’t take any chances, disorientation and dizziness caused by sleep deprivation can cause panic, no matter how well prepared you are for your exam.

Make flashcards: Something that is bound to give every other student an anxiety attack is thinking about concepts at the last moment and panicking when something can’t be immediately recalled the night before or even immediately before the exam. One way this can be taken care of is to make flashcards with little study notes and keep them handy, so that you can give them a quick glance whenever you want, instead of thinking yourself into a panic attack and getting anxious at the last moment.

At the end of the day, the best thing you can do before an exam is be well prepared and remind yourself that it is just a small obstacle and not the end of the world.