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Random Cisco based networking questions - CCNA - Part 9

More network based questions and answers, part nine of the 2015 series, complete with wiki reference links for further reading :-)

1.  What TCP/IP layer are Telnet, FTP, TFTP and SMTP protocols associated with?

A) Application
B) Host-to-Host / Transport
C) Internet
D) Network Access

2. What is not a main switch function?

A) Address learning
B) Frame forwarding
C) Packet forwarding
D) Loop avoidance

3. What layer of the OSI model segments and reassembles data from upper-layer applications and brings them together in the same data stream?

A: Presentation
B: Session
C: Transport
D: Network
E: Data Link

4. VLAN trunk protocol is responsible for?

A) Tracking and monitoring VLANS
B) Consistent VLAN configuration
C) Trunking VLANs across mixed networks
D) Reporting New VLANs
E) All of the above
5. If you are trunking between non-Cisco switches what frame tagging standard should you adopt?

A) 802.1q
B) ISL
C) 802.3q
D) VTP

6. If your switch uses shared memory buffering, what would happen if a packet could not be delivered because of a busy destination port?

A) It would delay transmission of all packets in memory
B) It would be sent to the destination port anyway
C) It would wait in a queue while all other packets in memory are transmitted
D) It would drop the packet after an allocated time

7.What is the equivalent of the TCP/IP Network Access layer in the OSI Reference layer?

A) Network
B) Data Link
C) Data Link and Physical
D) Physical
E) Transport

8. What is the Spanning Tree forward delay?

A) The time that is spent in the Listening and Learning states
B) 50 seconds
C) Time taken for a switch to go from Listening to Forwarding
D) Time taken for a switch to go from Blocking to Forwarding



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1. Answer: A

http://en.wikipedia.org/wiki/Internet_Protocol_Suite

2.  Answer: C 

Switches are layer 2 devices and do not look at layer 3 packets.

3. Answer: C

http://en.wikipedia.org/wiki/Transport_Layer

4. Answer: E

VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that manages the addition, deletion, and renaming of Virtual Local Area Networks (VLAN) on a network.

http://en.wikipedia.org/wiki/VLAN_Trunking_Protocol

5. Answer: A

ISL is a Cisco proprietary VLAN tagging protocol and therefore if you have a multi-vendor switch network you will need to choose the IEEE 802.1q standard instead of ISL.


6. Answer: C

The area of memory where the switch stores the data is called the memory buffer.
The memory buffer can use two methods for forwarding frames:
 
port-based memory buffering
shared memory buffering

In port-based memory buffering frames are stored in queues that are linked to specific incoming ports.

Shared memory buffering deposits all frames into a common memory buffer which all the ports on the switch share.

 7. Answer: C 

The link layer has the networking scope of the local network connection to which a host is attached. It is the lowest component layer of the Internet protocols, as TCP/IP is designed to be hardware independent. As a result, TCP/IP may be implemented on top of virtually any hardware networking technology.

http://en.wikipedia.org/wiki/TCP/IP_model#OSI_and_TCP.2FIP_layering_differences

8. Answer: A

Forward delay — The time that is spent in the listening and learning state, 15 sec by default, but you can tune the time to be between 4 and 30 sec.




Stay tuned for more coming soon :-)

Malware types explained.

The amount of cyber attacks is on the rise across the globe,  Here is a quick refresher on what the different types are.

Spyware.

 This malicious software keeps an eye on your computer use without your knowledge. It collects a variety of data, depending on its design. Some forms of this malware are actually legal, often bundled with free software; it monitors your web browsing habits, uploading the data to advertising servers.

Ransomware.

This new type of malware holds your computer or files hostage and demands a payment. Some forms may simply display a pop-up demanding money before you can continue using your computer. More harmful versions encrypt your files, rendering you helpless unless you’ve got backup.

The Trojan, or Trojan Horse. 

This type of malware disguises itself as a legitimate file. When you download and run the program, the malware runs in the background, allowing third parties to access your computer. This malware is often used to monitor activity on your computer, or to link your computer to a botnet.

The Virus. 

This malware copies itself by infecting other files. It can do many different things — watch in the background and steal your passwords, display advertisements, or just crash your computer — but its key characteristic is how it spreads: by infecting programs on your computer. When you run the program on another computer, the virus will infect programs on that computer, and so on.

The Worm.

 This malware spreads in a unique way. Rather than infecting files and relying on human activity to propagate, it spreads over computer networks of its own accord. It can do any number of harmful things once it infects a computer.

Malvertising. 

This term describes the use of online advertising to spread malware.

Random Cisco based networking questions - CCNA - Part 8

Here are another set of Random networking questions to ponder, good start for September :-)

I saw Bloke with a bumper sticker saying: "I am a veterinary surgeon, therefore I drive like an animal." Suddenly I realised how many gynecologists and proctologists there are on the roads.:-)

1. What is Cisco's default NAT table entry timeout (translation timeout)?

A: 1 hour
B: 12 hours
C: 24 hours
D: 36 hours
E: 48 hours

2. What layer of the OSI model is responsible for multiplexing upper-layer applications, establishing sessions and tearing down virtual circuits?

A: Presentation
B: Session
C: Transport
D: Network
E: Data Link

3. What is port 20 used for?

A: FTP data
B: FTP program
C: Telnet
D: SMTP
E: TFTP

4. Extended ACL allow you to filter Application layer traffic.

A: True
B: False

5. What command would you use to erase the startup config of a router?

A: erase nvram
B: erase flash
C: delete startup
D: erase startup
E: delete run

6. What is the reserved address space for a Class B network?

A) 10.0.0.0 - 10.255.255.255
B) 20.0.0.0 - 20.255.255.255
C) 172.16.0.0 - 172.31.255.255
D) 192.168.0.0 - 192.168.255.255
E) 208.168.0.0 - 208.168.255.255

7. What is responsible for ensuring a router is functional and the interfaces are present on booting?

A) Bootstrap
B) POST
C) ROM monitor
D) NVRAM
E) Configuration register

8. Store and forward switching method is best described by which of the following?

A) The entire frame is received before forwarding is commenced
B) Forwards frame after receiving destination address
C) Filters out collision packets by waiting for the first 64 bytes of data

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1. Answer: C

When an entry is placed into the NAT table a timer begins, the duration of this timer is called the translation timeout, defaulted to 24 hours on Cisco routers.

2. Answer: C

http://en.wikipedia.org/wiki/Transport_Layer

3. Answer: A

File Transfer Protocol (FTP) is a network protocol used to copy files from one host to another over a TCP/IP-based network.
A client makes a TCP connection to the server's port 21. This connection remains open for the duration of the session called the control connection, with a second connection, called the data connection, opened by the server from its port 20 to a client port required to transfer file data.

4. Answer: A

To filter Application layer traffic using extended ACLs, first specify TCP, then the port number of the Application layer protocol.

5. Answer: D

To erase the startup configuration use the following command:

Router#erase startup-config
or
Router#erase startup

6. Answer: C 

http://en.wikipedia.org/wiki/Private_network#Private_IPv4_address_spaces

7.  Answer: B

POST (Power-on-self-test) stored in ROM performs a basic router health-check on booting.

8. Answer: A

Store and forward switching method is known as store and forward because the switch will store the incoming data frame in its internal buffer, then when the complete frame has been received the switch will then run a Cyclic Redundancy Check (CRC) against the frame. If the CRC passes, the switch will then look up the destination MAC Address in its MAC filter table to forward it on to its destination.

How did you go?  stay tuned for more coming soon :-)

135 years of uptime

That equates to over 135 years.... pretty impressive, obviously a software bug but leads to interesting notion that it was around in 1880, the same time as the following:

Jan 27th 1880 - Thomas Edison patents electric incandescent lamp

Jun 1st 1880 - 1st pay telephone installed 
(In 1960, the Bell System installed its millionth pay telephone)

Jun 28th 1880 - Ned Kelly the Australian bushranger captured at Glenrowan.

Aug 2nd 1880 - British Parliament officially adopts Greenwich Mean Time (GMT)

Anatomy of the Internet of Things

The Internet of Things (IoT) is essentially a network of physical objects connected via the Internet, a buzzword for a new technology landscape that is reshaping the way we live and work. But is its potential understood and are we prepared for a new wave of industrial revolution?

The “things” are physical entities whose state or identity is capable of being relayed to a connected infrastructure. Almost anything to which a sensor can be attached – a plant, a cow in a field, the refrigerator in your home, a lamppost in the street or shipping container – can become a node or an endpoint in the IoT.





Sensors are components of “things’ that both collate and disseminate critical data on such things as temperature, altitude, velocity, illumination, motion, power, humidity, blood sugar, air quality, soil moisture or location… you name it. Mankind and technology are revolutionizing products and services, that were once analog and mechanical to complex systems that combine hardware, sensors, data storage, microprocessors, software and connectivity in multitude of ways.

These so-called smart or connected products have been made possible thanks to vast improvements and declining costs in data-processing power and device miniaturization, along with very sophisticated layered security. The products use sensors that can communicate either directly with the internet or with internet-connected devices, and by tapping ubiquitous wireless connectivity. Further, the software needed to analyze this data has improved dramatically, opening to the door to a new hyper-connected era of competition and growth.

Imagination is more important than knowledge.

- Albert Einstein - 1879-1955, Theoretical Physicist

Random Cisco based networking questions - CCNA - Part 7

Here is another set of network based questions and answers to get the grey matter ticking.. have fun :-)




1. STP will work on which of the following devices?

A) Hub
B) Router
C) Switch
D) Repeater

2. What command would you use copy the current configuration to a TFTP host?

A) copy flash tftp
B) copy run tftp
C) copy tftp flash
D) copy nvram tftp

3. You are designing a subnet mask for the 172.22.0.0 network. You want 11 subnets with up to 3300 hosts on each subnet. What subnet mask should you use?

4. What would you do if you're locked out of a router because you forgot the password?

A) Call Cisco support
B) Issue the show run command to view the password
C) Perform the password recovery procedure
D) Press the reset button on the back of the router
5. What does Serial 0 is up, line protocol is down indicate?

A) Keepalive or framing issue
B) Carrier detect is not present
C) The interface is shutdown
D) The interface is functioning correctly

6. With full-duplex Ethernet no collisions can occur.

A) True
B) False

7. How would you disable CDP on a Cisco router or switch?

A) disable cdp
B) shutdown cdp
C) no cdp enable
D) no cdp run
E) You cannot disable CDP

8. What type of ACL is this and what is it performing?

Router(config)#access-list 150 deny tcp any host 172.32.14.2 eq 25

A) Standard ACL, deny all SMTP traffic to host 172.32.14.2
B) Standard ACL, deny all Telnet traffic to host 172.32.14.2
C) Extended ACL, deny all SMTP traffic to host 172.32.14.2
D) Extended ACL, deny all Telnet traffic to host 172.32.14.2
E) Named ACL, deny all SMTP traffic to host 172.32.14.2
9. What does the trace response N mean?

A) Network unreachable
B) Not forwarded due to ACL restriction
C) Protocol unreachable
D) Port could not be reached

10. What is the maximum size of an Ethernet packet when the frames have ISL tagging?(Include the size of headers and CRC)

A: 64 bytes
B: 1500 bytes
C: 1518 bytes
D: 1522 bytes
E: 1548 bytes













1. Correct Answer C 

The Spanning Tree Protocol (STP) is a Data Link layer protocol that ensures a loop-free topology for a bridged LAN. 

Therefore STP will only operate on layer 2 devices such as bridges and switches.

2. Correct Answer B

The current configuration is known as the running-configuration (or 'run' for short). The copy command is in the format "copy " therefore copy from run to the tftp host (i.e. copy run tftp).

3. Correct Answer 255.255.240.0

4. Correct Answer C

To reset the password on a router interrupt the boot sequence, change the configuration register, reboot, copy startup-config to running-config and change the password.  Then reset the configuration register.

5. Correct Answer A

The various states of an interface:

Serial0 is up, line protocol is up - The interface is functioning correctly.

Serial0 is down, line protocol is down - This message usually represents a physical interface problem. The cable may be disconnected. This can also occur if this interface is connected to another router whose interface has been shutdown.

Serial0 is up, line protocol is down - The Physical layer connectivity is not the issue. The line protocol being down is either a clocking issue (keepalives) or a mismatch of the frame types being used on connected devices.

Serial0 is administratively down, line protocol is down - The interface has been manually shutdown using the shutdown command.

6. Correct Answer A

http://en.wikipedia.org/wiki/Full-duplex_Ethernet

7. Correct Answer D

To turn off CDP use the no cdp run command from the global configuration mode.

8. Correct Answer C

Router(config)#access-list 150 deny tcp any host 172.32.14.2 eq 25

Port 25 is SMTP. This extended ACL denies traffic from any source to host 172.32.14.2.

9. Correct Answer A

Cisco Trace Command Response Codes

Response Meaning
 * Timed out
 !H router received packet but did not forward it
 N network unreachable
 P protocol unreachable
 U port unreachable

10. Correct Answer: E

Cisco's proprietary VLAN tagging (ISL) has a maximum frame size of 1548 bytes.
IEEE 802.1q VLAN tagging has a maximum frame size of 1522 bytes.

Stay tuned more to come - have a great day.

I remind myself every morning: Nothing I say this day will teach me anything. 

So if I'm going to learn, I must do it by listening.
Larry King

How to detect phishing emails.

A timely reminder - please share 

 

Australia-US project achieves SDN routing breakthrough

 

Software-defined networking reaches internet scale.

The Australian Academic Research Network (AARNet) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) have demonstrated internet-scale software-defined network routing to the United States, using open source components.

Using a high throughput programmable Corsa OpenFlow DP6410 data plane, the Australian institutions set up a production SDN-based peering router with a switch deployed in AARNet's data centre in Haymarket, Sydney, and an Open Network Operating System (ONOS) application 15km away in Marsfield.

The Australian side has been peering for a month with the Vandervecken SDN router at the US Department of Energy's research Energy Sciences Network (ESnet) situated at the University of California, Berkeley, over a trans-pacific connection.


Read more: http://www.itnews.com.au/News/403686,australia-us-project-achieves-sdn-routing-breakthrough.aspx#ixzz3ZhWwzMUN

Random Cisco based networking questions - CCNA - Part 6

 Here's another half a dozen random networking questions to get the grey matter ticking :-)



1. Which switching mode is the most likely to forward frames containing errors?

A) FIFO
B) Modified Cut-Through
C) Store-and-Forward
D) Cut-Through
E) Fragment-Free

2. Where would you place standard access lists?

A) As close to the destination as possible
B) As close to the source as possible

3. Frame tagging is used to identify...

A) The intended recipient of a frame
B) The IP address of the frame
C) The source of the frame
D) The VLAN ID of the frame
E) The trunking method

4. When each network segment uses a different subnet mask this is referred to as...

A) Classful routing
B) Classless routing

5. A CIDR value of /12 equates to what subnet mask?

A) 255.0.0.0
B) 255.128.0.0
C) 255.192.0.0
D) 255.224.0.0
E) 255.240.0.0

6. How would you copy the IOS to a TFTP server?

A) Router(config)#copy ram tftp
B) Router(config)#copy tftp flash
C) Router#copy flash tftp
D) Router#copy tftp flash
E) None of the above

1.  Answer D 

Cut-Through switching is also referred to as Fast Forward.

When in cut-through mode the switch waits for the destination MAC Address to be received. Once the MAC Address is known the switch refers to its MAC filter table to determine which port the frame should be forwarded out. The switch forwards the frame even before the entire frame has arrived.

Frames with and without errors are forwarded in cut-through switching, leaving the error detection of the frame to the intended recipient.

2. Answer A

Standard access lists only filter based on source address so they have to be placed as close to the destination as possible.

3. Answer D

Frame tagging is used to tags frames on trunked links to identify what VLAN they belong to.

http://en.wikipedia.org/wiki/Virtual_LAN#Protocols_and_design

4. Answer B

http://en.wikipedia.org/wiki/Classful_network

5. Answer E

http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#Assignment_of_CIDR_blocks

6. Answer C

It is a good practice to backup your existing system image to the TFTP server using the copy flash tftp command.  I personally use Pumpkin or Solarwinds TFTP servers, but there are may other types around.

 Stay tuned for more updates, and let me know if you find these useful or any errors 

Please share around if you find these questions of value.

   “Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for.”
? Socrates