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

Random Cisco based networking questions - CCNA - Part 5

Another half a dozen random networking questions for 2015 with a more routing protocol focus this time, 

enjoy :-).

1. Triggered updates (in a routing protocol) are used to speed the convergence process?

A) True
B) False

2. What class of routing protocol is EIGRP?

A) Link state
B) Distance vector
C) Hybrid

3. What is the administrative distance of OSPF?

A) 110
B) 1
C) 120
D) 90
E) 100

4. 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

5. What is required for VTP to communicate VLAN information between switches?

A) VTP domain must be identical on all switches
B) One switch needs to be a VTP server
C) A router is required
D) Both A and B are correct
E) None of the above

6. What is the structure of the MAC address?

A) 32 bit network ID + 32 bit host ID
B) 14 bit vendor code + 6 bit serial number
C) 24 bit vendor code + 24 bit serial number
D) Network + Host

Searching for what type of nic card you have in your PC? The easiest way is with the MAC address ( not the kind shown below :-)

A great link you should bookmark for Vendor/Ethernet/Bluetooth MAC Address Lookup and Search at MACFIND.  This allows you to match your MAC address to its vendor or a vendor to a MAC - I find it very useful :-).

http://www.coffer.com/mac_find/

1.  Answer A

A triggered update is sent immediately in response to a change in the network (e.g. A link going down). The router detecting the change immediately sends an update message to its adjacent routers, which then generate their own triggered updates. This process continues until the network converges. Triggered updates occurs independently from the regular routing updates and are intended to speed the convergence process.

2. Answer C

EIGRP is a hybrid routing protocol which uses a combination of distance vector and link state methods to determine the best path. EIGRP is considered an advanced distance vector protocol because EIGRP sends out only incremental updates.

3. Answer A

Administrative distance is used by Cisco routers to select the best path when there are two or more different routes to the same destination from two different routing protocols. Administrative distance defines the reliability of a routing protocol.

Routing Protocol	Administrative distance
Directly connected interface	0
Static route out an interface	1
Static route to next-hop address	1
DMNR - Dynamic Mobile Network Routing	3
EIGRP summary route	5
External BGP	20
Internal EIGRP	90
IGRP	100
OSPF	110
IS-IS	115
Routing Information Protocol (RIP)	120
Exterior Gateway Protocol (EGP)	140
On Demand Routing (ODR)	160
External EIGRP	170
Internal BGP	200
Floating Static Route (ex. DHCP-learned)	254
Unknown	255

(Note : An AD of 255 will cause a router to dump this route from its table)

4. Answer D

To erase the startup configuration use the following command:

Router#erase startup-config, or
Router#erase startup

5. Answer D

VTP requires the following to communicate VLAN information between switches.  The VTP domain must be identical on all switches and one switch needs to be a VTP server.

6. Answer C

MAC Addresses are 48 bits long and consist of a 24 bit vendor code and a 24 bit serial number.

More coming, please leave comments if you find any errors or want to debate an answer :-)

Random Cisco based networking questions - CCNA - Part 4

Welcome to part 4 of the random networking questions (Cisco based) series.  This set has a few extra spanning tree questions with detailed explanations, have fun :-)


1. What is the default time Bridge Protocol Data Units (BPDUs)  are sent and received by switches?

A) 2 seconds
B) 10 seconds
C) 30 seconds
D) 60 seconds

2. What does the following statement do?

Switch(config-if)#spanning-tree portfast disable

A) Disables spanning-tree on the switch port
B) Disable spanning tree on the switch
C) Changes the spanning-tree switch to portfast mode

3. What determines network addresses (IP) when data link addresses (MAC) are known?

A) Ping
B) ICMP
C) ARP
D) RARP

4. The Cisco Spanning Tree protocol is compatible with IEEE 802.1d?

A) True
B) False

5. What type of switch port can belong to multiple VLANS?

A) Access port
B) Trunk port
C) Voice access port
D) No port can belong to multiple VLANs

6.What will be the IP address of the second subnet given the following?

172.16.0.0 255.255.224.0 (Assume ip subnet-zero is enabled)

A.) 172.16.0.0
B.) 172.16.8.0
C.) 172.16.16.0
D.) 172.16.32.0
E.) 172.16.64.0

Speaking of IP, I sometimes use a simple little site that gives you your own IP and other internet connectivity details   - IP Chicken - handy link  :-)

1. Answer A

http://en.wikipedia.org/wiki/Spanning_tree_protocol#Bridge_Protocol_Data_Units_.28BPDUs.29

Bridge Protocol Data Units (BPDUs) frames are sent out as multicast messages regularly at multicast destination MAC address 01:80:c2:00:00:00. When Bridge Protocol Data Units (BPDUs) are received, the Switch uses a mathematical formula called the Spanning Tree Algorithm (STA) to know when there is a Layer 2 Switch loop in network and determines which of the redundant ports needs to be shut down.

Three types of Bridge Protocol Data Units (BPDUs) are Configuration BPDU (CBPDU), Topology Change Notification (TCN) BPDU and Topology Change Notification Acknowledgment (TCA).

2.  Answer A

The time Spanning Tree Protocol (STP) takes to transition ports over to the Forwarding state can cause problems. PortFast is a Cisco network function which can be configured to resolve this problem by disabling STP from the switchport, thus making it come up quicker.

3. Answer D

Reverse Address Resolution Protocol (RARP) is used by a host computer to request its IPv4 address from an administrative host (DHCP server), it provides the server with its hardware address (MAC address).

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


NOTE: Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway.

4.  Answer B

The original Spanning-Tree protocol was created by Digital Equipment Corporation (DEC) which is now part of Compaq. The IEEE created its own version called IEEE 802.1d which is not compatible with the original version.

Cisco enhanced the original 802.1d specification with features such as Uplink Fast, Backbone Fast, and Port Fast to speed up the convergence time of a bridged network. However these new features are proprietary, and can only be configured on Cisco switches.

5. Answer B

Ethernet interfaces can be configured either as access ports or trunk ports. Trunks carry the traffic of multiple VLANs over a single link and allow you to extend VLANs across the network.

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

6. Answer D 

The subnet block size is 256 - 224 = 32
The first subnet will be subnet zero 172.16.0.0
The second subnet will be 172.16.32.0

How did you go? I find a quick review of the questions and answers helps cement the basics and refresh the memory  - I hope these help, stay tuned for more...

The secret of life is not to do what you like but to like what you do.
By: Anonymous

Random Cisco based networking questions - CCNA - Part 3

Welcome to part 3 of the random networking questions (Cisco based) series.

Ready to get the brain tickin? Lets go!

1. What Cisco IOS enhanced editing command end the configuration mode and returns to EXEC?

A) Ctrl+Z
B) Ctrl+W
C) Ctrl+F
D) Esc+F
E) Tab

2, Which devices operate at the Data Link layer?

A) Switch
B) Bridge
C) Repeater
D) Router
E) Both A and B

3. Triggered updates are used to speed the convergence process?

A) True
B) False

4. 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

5. What is the function of asymmetric switching?

A) To prioritise bandwidth to nodes that need it
B) To prevent bottlenecks on the port a server is connected to
C) To allow RAS clients to connect to the network

6. PPP can be used over what types of serial connections?

A) Synchronous
B) Asynchronous
C) Both
D) Neither










1. Answer A

Keyboard Shortcut Actions (I've published this before but thought it worthy to remind :-)

Up Arrow Displays your previous commands.  (command history)
TAB Key Completes a partially typed CLI commands.
CTRL+Z Takes you back to Privileged EXEC Mode.

CTRL+A Places the cursor at the beginning of a line.
CTRL+E Places the cursor at the end of a line.
CTRL+R Redisplays the current command line.
CTRL+W Erases a word (behind the cursor).
CTRL+U Erases an entire line.

2. Answer E

Bridges and switches filter network traffic based on the MAC address (hardware address) and are Data Link layer devices.

A Repeater does not apply any filtering and is therefore a Physical Layer device.

Routers forward packets based on logical network addresses are are Network Layer devices.

3. Answer A

A triggered update is sent immediately in response to a change in the network (e.g. A link going down). The router detecting the change immediately sends an update message to its adjacent routers, which then generate their own triggered updates. This process continues until the network converges. Triggered updates occurs independently from the regular routing updates and are intended to speed the convergence process.

4. 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.

5. Answer B

An asymmetric switch provides switched connections between ports of different bandwidths.
Asymmetric switching is optimized for client-server traffic where multiple clients simultaneously communicate with a server, requiring more bandwidth dedicated to the server port to prevent a bottleneck at that port.

6. Answer C

Point-to-Point Protocol (PPP) can be used over ISDN (synchronous) and dial-up (asynchronous) connections.

All over the place that time - stay tuned for the next batch - coming soon:-)

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

Random Cisco based networking questions - CCNA - Part 2

Part 2 in the series of random networking questions for 2015, to keep you current or stimulate thought..

 1. Where would you place more specific tests in your access list?

A) At the top
B) At the bottom
C) Placement doesn't matter


2. Routers are what by default?

A) DTE devices
B) DCE devices

3. Which WAN protocol is capable of carrying video, Circuit Switched Data And Telephone Services using normal phone network?

A) Frame Relay
B) ISDN
C) PPP
D) ISL

4. What protocol range would you use for IP in ACLs?

A) 1-99
B) 800-899
C) 200-299
D) 1000-1099

5. What IP address will test the internal loopback of a node?

A) 127.0.0.1
B) 255.255.255.255
C) 0.0.0.0
D) 126.0.0.1
E) 127.0.0.0

6. When each network segment uses a different subnet mask this is refered to as...

A) Classful routing
B) Classless routing












1. Answer A

Always organise your access lists so the more specific tests are at the top.

2. Answer A

A router is configured as a DTE by default. If a clock rate speed is not specified, the router is configured as a DTE. If a clock rate speed is specified, the router is configured as a DCE.

DTE = Data Terminal Equipment
DCE = Data Communications Equipment

 3. Answer B

ISDN (Integrated Services Digital Network) is a set of standards for simultaneous digital communications (voice, video, data) over the traditional circuits of the public switched telephone network.

4. Answer A

Standard Cisco IOS Help output
Router#configure terminal
Router(config)#access-list ?
 <1-99>  IP standard access list
 <100-199> IP extended access list
 <1100-1199> Extended 48-bit MAC address access list
 <1300-1999> IP standard access list (expanded range)
 <200-299> Protocol type-code access list
 <2000-2699> IP extended access list (expanded range)
 <700-799> 48-bit MAC address access list
 rate-limit Simple rate-limit specific access list

5.  Answer A

127.0.0.1 is the loopback address in IP, it is a test mechanism for network adapters. Messages sent to 127.0.0.1 do not get delivered to the network. The NIC intercepts all loopback messages and returns them to the sending application.

6. Answer B

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

More coming, please leave comments if you find any errors or want to debate an answer :-)

"Whatever you are, be a good one."

Abraham Lincoln

Random Cisco based networking questions - CCNA - Part 1

The first half a dozen of random networking questions to get you thinking in 2015 :-)

Enjoy,,

1. Where would you place extended access lists?

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

2. Bridges can only have one spanning tree instance, while switches can have many.

A) True
B) False

3. What would happen if you put the following ACL on an interface?

access-list 1 deny 172.168.0.1
access-list 1 deny 192.5.2.1

A) All traffic from 172.168.0.1 and 192.5.2.1 would be denied
B) All traffic would be denied
C) Nothing
D) These are not Cisco IOS ACL commands

4. Which layer of the OSI model is concerned with Media Access Control addresses?

A) Layer 1
B) Datalink layer
C) Application Layer
D) Session Layer
E) Transport Layer

5. What do the IOS commands below achieve?

Router(config)#access-list 5 permit 172.5.15.2
Router(config)#line vty 0 4
Router(config-line)#access-class 5 in

A) Create an extended ACL to only permit host 172.5.15.2 to connect to VTY
B) Create a standard ACL to only permit host 172.5.15.2 to connect to VTY
C) Create an extended ACL to only permit hosts on the network 172.5.15.2 to connect to VTY
D) Create a standard ACL to only permit hosts on the network 172.5.15.2 to connect to VTY
6. 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









1. Answer B 

Extended access lists are much more granular than standard ACLs, you can block specific ports or protocols.

To avoid unnecessary traffic on your network place them as close to the source as possible.

2. Answer A (true)

Bridges are software based and can only have one spanning-tree instance per bridge, while switches are hardware based and can have many.

3. Answer B

People forget the not shown the automatic deny any any on the tail end of any access list :-)

4. Answer B

Media Access Control is a sublayer of the Data Link Layer specified within the OSI model. It provides addressing and channel access control.  The hardware that implements the MAC is referred to as a Media Access Controller.

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

5. Answer B

Router(config)#access-list 5 permit 172.5.15.2
Router(config)#line vty 0 4
Router(config-line)#access-class 5 in

This standard access list permits only the host 172.5.15.2 to connect to your VTY telnet line.

6. 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.

How did you do?? stay tuned more coming or check out the previous posts :-)

"If you want success, then don't rely on other people to do what YOU can do!" 

Sasha Azevedo

Data retention for eternity.

The next breed of solid state drives maybe ???

Researchers at a Zurich university have succeeded in storing and retrieving digital information in DNA segments, the molecules that encode genetic information, a breakthrough that could lengthen the lifespan of information storage by millions of years.

In a paper published by Angewandte Chemie, the team of researchers from Eidgenössische Technische Hochschule described how they managed to translate the 1291 Federal Charter of Switzerland and Archimedes' The Methods of Mechanical Theorums, a total of 83 kilobytes of information, into 4991 segments of DNA.

Researchers in the United States were able to encode a 5.27 megabyte book with images into DNA two years ago

Read more: http://www.itnews.com.au/News/400620,researchers-make-dna-data-storage-breakthrough.aspx#ixzz3S4edCjXP

A new round of Network Q&A will be coming soon - stay tuned....

Ian