Let's test your knowledge of the default-information originate command, Setup Mode, and VPNs with these Cisco certification exam practice questions!
CCNA Certification:
What's the main difference between the default-information originate command with and without the always option? Be specific.
Answer: Let's use IOS Help to look at our options for this command.
R1(config)#router ospf 1
R1(config-router)#default-information originate ?
always Always advertise default route
metric OSPF default metric
metric-type OSPF metric type for default routes
route-map Route-map reference
The always option allows the router to propagate a default route without actually having one in its routing table. Without that option, the router must have a default route in its table in order to advertise one.
CCENT Certification:
You're using Setup Mode to configure a Cisco router. You decide halfway through that you'd rather write the configuration at the CLI. How can you exit Setup Mode and not save the configuration you're in the process of writing?
Answer: Use the ctrl-c keystroke combination to exit Setup Mode without saving your configuration. You'll then be placed back at the command prompt.
CCNA Security Certification / CCNP ISCW Exam:
The SA state of your VPN is shown as QM_IDLE. Is this good? If not, what do we need to do to resolve the issue?
Answer: There is no issue - that's what we want the SA state to be!
CCNP Certification / BSCI Exam:
What command allows you to add protocols to those forwarded by the ip helper-address command? And just to review, what protocols are forwarded by the helper-address command?
Answer: Nine common UDP service broadcasts are "helped" by default:
TIME, port 37
TACACS, port 49
DNS, port 53
BOOTP/DHCP Server, port 67
BOOTP/DHCP Client, port 68
TFTP, port 69
NetBIOS name service, port 137
NetBIOS datagram service, port 138
IEN-116 name service, port 42
You can use the ip forward-protocol command to add any UDP port number to the list.
To remove protocols from the default list, use the no ip forward-protocol command.
R1(config)#ip forward-protocol udp 123
R1(config)#no ip forward-protocol udp 137
R1(config)#no ip forward-protocol udp 138
CCNP Certification / BCMSN Exam:
You've just enabled password encryption on a Cisco switch. When you attempt to view the VTP password, what will you see? And what command did you run to see the VTP password?
Answer: You'll see the password clear as day - the password encryption service has no effect on the VTP password. You can view the password with the "top-secret" show vtp password command.
CCNP / ONT Exam:
What's the major difference between RED and WRED? (The answer "one letter" is not acceptable.)
Answer: RED is a major improvement over Tail Drop, but it still doesn't give us a great deal of control over the entire queueing and dropping process. With one simple word, though, we do gain that control - when we use Weighted Random Early Detection (WRED).
Look for other Cisco practice exams and illustrated tutorials on my website!
Wednesday, August 6, 2008
Cisco CCNA, CCNP, and Security Practice Exam - OSPF Neighbors, Fail Closed, SDM, and More!
Here's a free Cisco certification exam practice set for you! Answers are at the bottom of the article. No peeking!
CCNA Certification:
In an OSPF hub-and-spoke NBMA network, which router(s) require the neighbor command?
A. The DR
B. The DROthers
C. The BDR
D. All of these
E. None of these
CCNA Security Certification / CCNP ISCW Exam:
You're configuring IPS in SDM, and you just enabled the Fail Closed option. What's the net effect?
CCNP Certification / BSCI Exam:
Which of the following are Cisco recommendations for OSPF deployments?
A. No router in more than three areas.
B. No area should contain more than 50 routers.
C. No router should have more than 60 neighbors.
D. No ABR should run more than one OSPF process.
CCNP Certification / BCMSN Exam:
You're examining the lights on a Cisco Aironet card. The green light is blinking slowly, the amber light is off. What does this generally indicate?
CCNP / ONT Exam:
What is Global Synchronization? Is it a benefit or a detriment to network performance?
Here are the answers!
CCNA: Answer: A. The DR requires the neighbor command. It will not hurt anything to have it configured on the DROthers in real-world networks, but I wouldn't put it there on exam day. There are no BDRs in an OSPF hub-and-spoke network.
ISCW / CCNA Security: Answer: Here's the exact description of Fail Closed from SDM itself:
"By default, while IOS compiles a new signature for a particular engine, it allows packets to pass through without scanning for the corresponding engine. Enable this option to make IOS drop packets during the compilation process."
Fail Closed is disabled by default.
BSCI: Answer: A, B, C, D. Those are all Cisco best practices for OSPF.
BCMSN: Answer: Here's a quick review of what those lights are and what the different combinations indicate.
We have two lights on a Cisco Aironet card. The green light is the Status LED, and the amber light is the Activity LED. We've got quite a few combinations with those two lights, so let's take a look at what each of the following LED readouts indicates.
Status off, Activity off - Naturally, this means the card isn't getting power!
Status blinking slowly, Activity off - the adapter's in Power Save mode.
Status on, Activity off - adapter has come out of Power Save mode.
Both lights blinking in an alternating fashion - adapter is scanning for its network.
Both lights blinking slowly at the same time - adapter has successfully associated with an AP (or other client if you have an Ad Hoc network)
Both lights blinking quickly at the same time - adapter is associated and is sending or receiving data
ONT: Answer: Here's a review of tail drop and how it can cause Global Synchronization. Usually synchronization is good, but this kind isn't!
When the queue is full, packets that are trying to queue up for transmission literally have nowhere to be put! These packets are then subject to tail drop, which is a fancy way of saying "you're being dropped because we have no place to put you".
You know that TCP has a detection and recovery scheme when it comes to missing segments, so tail drop is no big deal, right? Quite the opposite, it's a huge deal.
The problem starts innocently enough, as the senders realize their TCP packets are being dropped. As we'd expect, the senders then throttle back on their transmission speed. After doing so, the senders will then gradually speed their transmission rates back up.
As multiple senders increase their transmission rates, the queue will fill up again, and the senders will again almost simultaneously slow their transmission rates, followed by another near-simultaneous increase.
As a result of this global synchronization, the links are perpetually in one of two states - congested or underused. Basically, the network ends up being either hammered or not being used to its full potential, and those are both circumstances we want to avoid.
One way to avoid global synchronization is though the use of Random Early Detection (RED).
Look for more Cisco practice exams on my website as well as this one!
CCNA Certification:
In an OSPF hub-and-spoke NBMA network, which router(s) require the neighbor command?
A. The DR
B. The DROthers
C. The BDR
D. All of these
E. None of these
CCNA Security Certification / CCNP ISCW Exam:
You're configuring IPS in SDM, and you just enabled the Fail Closed option. What's the net effect?
CCNP Certification / BSCI Exam:
Which of the following are Cisco recommendations for OSPF deployments?
A. No router in more than three areas.
B. No area should contain more than 50 routers.
C. No router should have more than 60 neighbors.
D. No ABR should run more than one OSPF process.
CCNP Certification / BCMSN Exam:
You're examining the lights on a Cisco Aironet card. The green light is blinking slowly, the amber light is off. What does this generally indicate?
CCNP / ONT Exam:
What is Global Synchronization? Is it a benefit or a detriment to network performance?
Here are the answers!
CCNA: Answer: A. The DR requires the neighbor command. It will not hurt anything to have it configured on the DROthers in real-world networks, but I wouldn't put it there on exam day. There are no BDRs in an OSPF hub-and-spoke network.
ISCW / CCNA Security: Answer: Here's the exact description of Fail Closed from SDM itself:
"By default, while IOS compiles a new signature for a particular engine, it allows packets to pass through without scanning for the corresponding engine. Enable this option to make IOS drop packets during the compilation process."
Fail Closed is disabled by default.
BSCI: Answer: A, B, C, D. Those are all Cisco best practices for OSPF.
BCMSN: Answer: Here's a quick review of what those lights are and what the different combinations indicate.
We have two lights on a Cisco Aironet card. The green light is the Status LED, and the amber light is the Activity LED. We've got quite a few combinations with those two lights, so let's take a look at what each of the following LED readouts indicates.
Status off, Activity off - Naturally, this means the card isn't getting power!
Status blinking slowly, Activity off - the adapter's in Power Save mode.
Status on, Activity off - adapter has come out of Power Save mode.
Both lights blinking in an alternating fashion - adapter is scanning for its network.
Both lights blinking slowly at the same time - adapter has successfully associated with an AP (or other client if you have an Ad Hoc network)
Both lights blinking quickly at the same time - adapter is associated and is sending or receiving data
ONT: Answer: Here's a review of tail drop and how it can cause Global Synchronization. Usually synchronization is good, but this kind isn't!
When the queue is full, packets that are trying to queue up for transmission literally have nowhere to be put! These packets are then subject to tail drop, which is a fancy way of saying "you're being dropped because we have no place to put you".
You know that TCP has a detection and recovery scheme when it comes to missing segments, so tail drop is no big deal, right? Quite the opposite, it's a huge deal.
The problem starts innocently enough, as the senders realize their TCP packets are being dropped. As we'd expect, the senders then throttle back on their transmission speed. After doing so, the senders will then gradually speed their transmission rates back up.
As multiple senders increase their transmission rates, the queue will fill up again, and the senders will again almost simultaneously slow their transmission rates, followed by another near-simultaneous increase.
As a result of this global synchronization, the links are perpetually in one of two states - congested or underused. Basically, the network ends up being either hammered or not being used to its full potential, and those are both circumstances we want to avoid.
One way to avoid global synchronization is though the use of Random Early Detection (RED).
Look for more Cisco practice exams on my website as well as this one!
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