Wednesday, July 16, 2008

It's Wednesday, July 16, and here are the answers to yesterday's brand-new Cisco certification exam practice questions!


What's the main difference between a hub and a repeater?

A. A hub has more ports than a repeater.

B. A repeater has more ports than a hub.

C. A hub works at Layer 2 of the OSI model, where a repeater works at Layer 1.

D. A repeater works at Layer 2 of the OSI model, where a repeater works at Layer 1.

Answer: A. A hub is simply a multiport repeater. Both hubs and repeaters work at the Physical layer (Layer 1) of the OSI model.

CCNA Exam:

This isn't a Cisco command, but you still need to know it - what command resulted in the following output on a typical PC?

C:\> ?
Internet Address Physical Address Type bb-bb-bb-bb-bb-bb dynamic

Answer: That's the output of arp -a.

CCNA Security Exam and CCNP / ISCW Exam Question:

Describe an IP Spoofing attack.

Answer: You may remember from your ISDN studies that when an ISDN line was pretending to be up, it was said to be spoofing.

When a network intruder uses the IP address of a trusted device in order to gain access to your network, that's IP Spoofing.

IP Spoofing can be used against your network in several ways:

1. To inject a stream of malicious code and/or commands into your network

2. To trick legitimate network hosts into sending sensitive data to the attacker

3. As part of a reconnaissance attack, an attack that in itself may not be damaging, but is used to gather information for future, more destructive attacks.


Examine the following output and identify the true statements.


Neighbor ID Pri State Dead Time Address Interface 0 FULL/DROTHER 00:01:43 Serial0 0 FULL/DROTHER 00:01:35 Serial0

A. This output is the result of the show ip ospf command.

B. This output is the result of the show ip ospf neighbor command.

C. This output is the result of the show ip ospf all command.

D. R1 is likely the hub of a hub-and-spoke network.

E. R1 is likely a spoke of a hub-and-spoke network.

F. The OSPF interface priorities have been changed on the remote routers.

G. The OSPF interface priorities have not been changed.

Answers: B, D, F. We know this is the output of show ip ospf neighbor. Since the two neighbors are both DROTHERS and the adjacencies have been formed over Serial interfaces, that's a tipoff that we are on the hub of a hub-and-spoke network.

In a hub-and-spoke OSPF network the spokes will usually have their OSPF interface priority changed to zero from the default of 1.


What's the purpose of the following command?

SW1#show spanning-tree backbonefast
BackboneFast is enabled

Answer: The Cisco-proprietary feature Backbonefast can be used to help recover from indirect link failures.

The key word there is indirect. If a core switch detects an indirect link failure - a failure of a link that is not directly connected to the core switch in question - Backbonefast goes into action.

CCNP / ONT Exam:

What's the purpose of QoS preclassification?

Answer: Ads for loans and credit cards often mention that you've been "pre-qualified" for that loan or card, which means that you're guaranteed to get the credit without having to go through a long approval process. (No, I'm not about to ask you to sign up for a credit card.)

QoS Preclassification is something like that, since the original packet will be guaranteed to keep its original QoS value without copying that value to its new IP header.

I'll have some new questions for you later today!

To your success,

Chris Bryant
CCIE #12933

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