Wednesday, February 1, 2017

February networking question

The February edition of random networking questions.

Another 10 questions to get the grey matter ticking :-)

1. A flat network can be best described as...

A) Physically flat
B) One collision domain
C) One broadcast domain

2. Where does routing occur within the DoD TCP/IP reference model?

A. application
B. internet
C. network
D. transport

3. What layer of the OSI model provides the physical transmission of data, handles error notifications, network topology and flow control?

A) Physical
B) Data Link
C) Presentation
D) Session
E) Transport

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

A) True
B) False

5. A Cisco router is booting and has just completed the POST process. It is now ready to find and load an IOS image. What function does the router perform next?

A. It checks the configuration register.
B. It attempts to boot from a TFTP server.
C. It loads the first image file in flash memory.
D. It inspects the configuration file in NVRAM for boot instructions.

6. A CIDR value of /30 equates to what subnet mask?


7. 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

8. Which item represents the standard IP ACL?

A. access-list 110 permit ip any any
B. access-list 50 deny
C. access list 101 deny tcp any host
D. access-list 2500 deny tcp any host eq 22

9. Which two commands correctly verify whether port security has been configured on port FastEthernet 0/12 on a switch? (Choose two.)

A. SW1#show port-secure interface FastEthernet 0/12
B. SW1#show switchport port-secure interface FastEthernet 0/12
C. SW1#show running-config
D. SW1#show port-security interface FastEthernet 0/12
E. SW1#show switchport port-security interface FastEthernet 0/12

10. Which protocol can cause overload on a CPU of a managed device?

A. Netflow

1. Correct Answer C

A switched network can be described as a flat network because broadcasts are transmitted to every device.

2. Correct Answer B

The picture below shows the comparison between TCP/IP model & OSI model. Notice that
the Internet Layer of TCP/IP is equivalent to the Network Layer which is responsible for
routing decision.

3. Correct Answer B

4. Correct Answer A

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

5. Correct Answer A

Default (normal) Boot Sequence
Power on Router - Router does POST - Bootstrap starts IOS load - Check configuration
register to see what mode the router should boot up in (usually 0x2102 to read startupconfig
in NVRAM / or 0x2142 to start in "setup-mode") - check the startup-config file in
NVRAM for boot-system commands - load IOS from Flash.

6. Correct Answer D

7. 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.

8. Correct Answer B

The standard access lists are ranged from 1 to 99 and from 1300 to 1999 so only access
list 50 is a standard access list.

9. Correct Answers C and D

We can verify whether port security has been configured by using the “show runningconfig”
or “show port-security interface” for more detail. An example of the output of “show
port-security interface” command is shown below:

10. Correct Answer D

Sometimes, messages like this might appear in the router console:
%SNMP-3-CPUHOG: Processing [chars] of [chars]
They mean that the SNMP agent on the device has taken too much time to process a

How did you go? very random selection huh :-)

let me know if you found any errors in the comments, more coming .

“Don't cry because it's over, smile because it happened.”
Dr. Seuss

Tuesday, January 10, 2017

Networking questions part 1

I'm going to try to submit questions at least once a month this year (hopefully more often)

Here's the first batch, enjoy....

1. What layer of the OSI Reference Model sends and receives bits and specifies the electrical, mechanical, procedural and functional requirements for maintaining a physical link between end systems?

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

2. What Cisco IOS keyboard shortcut recalls the oldest command in the command history, beginning with the most recent command?

A) Ctrl+B
B) Ctrl+E
C) Ctrl+U
D) Ctrl+N
E) Ctrl+P

3. What does Router(config)# no access-list 1 command achieve?

A) Removes Access List 1
B) Disables ACL on interface 1
C) Nothing, this is not a Cisco command

4. When would an interface need a clock rate?

A) When the interface is DTE
B) When the interface is DCE

5, 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

6. What is the maximum number of subnets given the following?
(Assume ip subnet-zero is enabled)

A) 4
B) 8
C) 16
D) 32
E) 64

7. What is port 21 used for?

A) FTP data
B) FTP program
C) Telnet

8. What does the term "Logical address" refer to?
A) MAC address
B) Physical address
C) IP address
D) Link-layer address

9. What is the maximum number of hosts you can assign to a class C network if it is not subnetted?

A) 1024
B) 254
C) 32
D) 512
E) 65025

10. A router has two Fast Ethernet interfaces and needs to connect to four VLANs in the local network. How can you accomplish this task, using the fewest physical interfaces and without decreasing network performance?

A. Use a hub to connect the four VLANS with a Fast Ethernet interface on the router.
B. Add a second router to handle the VLAN traffic.
C. Add two more Fast Ethernet interfaces.
D. Implement a router-on-a-stick configuration.

1. Correct Answer E

2. Correct Answer E

Keyboard Shortcut Action

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.

3. Correct Answer A

If you wish to remove an access-list, you use the no access-list (list #) command.

4. Correct Answer B

Cisco routers are DTEs by default (Data Terminal Equipment). The DCE (Data Circuit-Terminating Equipment) at the other end of the connection must supply a clock rate to the DTE.

5. Correct 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.

6. Correct Answer A is a class C address.  The subnet mask implies 2 bits are borrowed.
22 = 4 subnets

7. Correct Answer B

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.

8. Correct Answer C

A Logical address is normally a 32-bit IP address assigned to each host in an IPv4 network.

A Physical address is a unique 48-bit flat address normally burned into the ROM of the NIC card, and therefore cannot be changed. It is divided into 24-bit vendor code and 24-bit serial address.

9. Correct Answer B

For class C the number of bits for host address portion is 8. So 2^8 -2 = 256-2 = 254 hosts.

10. Correct Answer D

A router on a stick allows you to use sub-interfaces to create multiple logical networks on a
single physical interface.

How did you go? If you disagree with any of my answers or find errors, please leave a comment. More coming soon..stay tuned :-)

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

Welcome to 2017

Time to start a new round of networking questions.  

This year I'm going to expand and include more different types of technologies,

However, Cisco will still be the main focus for the questions 
(mainly to keep my own brain ticking lol) 

Tuesday, September 20, 2016

Networking Questions 2016 Part 5

Here are some more very random networking questions based around the CCNA type of exam head scratchers... :-)

1. What type of NAT allows you to map multiple unregistered IP addresses to a single registered IP address?

A) Static NAT
B) Dynamic NAT
C) Overloading (Port Address Translation)

2. Each port on a switch is a separate broadcast domain?

A) True
B) False

3. Inter-Switch Link and IEEE 802.1Q are types of...

A) Spanning Tree Protocol
B) Trunking method
C) Ethernet
D) Routing protocol

4. What statement is not correct when talking about a shared-medium Ethernet LAN?

A) The data frame broadcast delivery nature of Ethernet can have a negative affect on performance
B) Adding repeaters and hubs to an Ethernet network can increase latency
C) Ethernet is a best-effort delivery service
D) Collisions are caused by CSMA/CD on an Ethernet network

5. What TCP/IP layer are TCP and UDP protocols associated with?

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

6. What IOS command would you issue in privileged-mode to change the Cisco router configuration stored on TFTP?

A) config t
B) config mem
C) config net
D) config tftp

Dodo Australia |ADSL|Wireless Broadband|Mobiles|Internet|Phone|Electricity|

1. Answer: C

PAT (Port Address Translation) allows you to map multiple unregistered IP addresses to a single registered IP address.

2. Answer: B

Switches create separate collision domains but a single broadcast domain.

3. Answer: B

Both Inter-Switch Link and IEEE 802.1Q are types of VLAN identification.  Inter-Switch Link (ISL) is a Cisco proprietary protocol whereas IEEE 802.1Q is a standard method of frame tagging.
4. Answer: D (did you get the "not"?)

Carrier Sense Multiple Access / Collision Detection (CSMA/CD) is a set of rules determining how network devices should respond when two devices try to use the shared medium simultaneously.

5. Answer: B

TCP and UDP protocols are associated with the Transport layer of the TCP/IP model, which is sometimes referred to as the "host-to-host transport layer".

Internet protocol suite examples:
Application layer
Transport layer
Internet layer
IP  (IPv4 · IPv6) · ICMP · ICMPv6 · ECN · IGMP · IPsec  
Link layer
ARP · NDP · Tunnels  (L2TP · PPP · MAC  (Ethernet · DSL · ISDN · FDDI ·

6. Answer: C

To change the router configuration stored on TFTP you use configure network (config net)

More random question 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

Saturday, September 17, 2016

IPV4 Subnetting Tips

It always takes a bit to get your head around subnetting for the first time, and even more to answer the exam questions they give as they often are designed to trick you.

For random IPV4 subnetting questions to hone your skills, I suggest you bookmark:

Memorizing the tables help immensely,  although at first appearance they appear daunting.

/24 8 256 = 28 Large LAN
/25 7 128 = 27 Large LAN
/26 6 64 = 26 Small LAN
/27 5 32 = 25 Small LAN
/28 4 16 = 24 Small LAN
/29 3 8 = 23 Smallest multi-host network
/30 2 4 = 22 "Glue network" (point to point links)
/31 1 2 = 21 Point to point links (RFC 3021)
/32 0 1 = 20 Host route


Remember the binary number doubles for each bit.  2, 4, 8, 16, 32, 64, 128, 256 etc

Also remember 8, 16, 24, 32 for the 8 bit block sizes. 

To find the block size, find the first octet that is not 255, then subtract it from 256... eg subnet mask of ...256 - 224 = block size of 32 

Subtract 2 from the block size to get the number of hosts eg 32 - 2 = 30 host IP.
(network and broadcast addresses cannot be used for user IP)

For the slash format, eg /27 subtract 27 from 32 to give a remainder of 5
Then if we count up 5 times doubling, 2, 4, 8, 16, 32 we get to the same block size of 32.

We also see that 224 is equal to 3 subnet bits taken from the octet ( 11100000) in a C class subnet, this will equal 8 subnets (allowing for subnet zero) 1, 2, 4 = 7+1 = 8 subnets.

Some providers have questions relating to old routing kit that did not allow the use of the all "1" subnet or all the "0" subnet (known as 'subnet zero').On all new Cisco routers, the number of subnets is calculated using the formula of 2^n by default. However, for legacy routers network engineers use 2^n - 2 to comply with the almost obsolete RFC 1878 standard. 

Some text books and courses that relate to old routing equipment also refer to the old formula as do some Microsoft Learning courses. If you're planning to take a non-Cisco exam that involves subnetting you should make sure you understand the 'subnet zero' concept' and check what is considered the default correct formula by your examining board

Once you get the patterns 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, etc and the masks 255, 254, 252, 248, 240, 224, 192, 128 burnt in it will become way easier :-)

Networking Questions 2016 Part 4

Been a while since we've stretched the grey matter, time to get to some more thinking with these random networking questions :-) Have fun.

1. In which layer of the OSI model does framing occur?

A) Layer 3
B) Physical layer
C) Application layer
D) Layer 2
E) Network layer

2. How would you view the current Cisco Configuration Register value?

A) show config-register
B) show reg
C) show config
D) show version

3. What does 'r' stand for in the capabilities of a Cisco device in the output of a show cdp neighbor command?

A) Repeater
B) Router
D) Host
E) Switch

4. Ethernet technology relates to which type of network?

E) All of the above

5. What is the numerical value of the Bridge Priority held by Catalyst switches?

A) 32500
B) 32768
C) 100
D) 1024
E) 32700

6. What OSI layer does the following refer to?

"Establishes availability of intended communication partners, establishes agreement on procedures regarding error recovery and data integrity and synchronizes networked applications"

A) Transport layer
B) Session layer
C) Datalink layer
D) Application layer
E) Presentation layer

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

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

8. Which of the following could be a valid MAC address?

A) 00-08-74-CE-B7-90

--> Ads

1. Answer: D

The protocol data unit (PDU) of the Data Link layer (Layer 2) is the frame.  Data passed down from the Network layer is framed at layer 2 before being sent on to the Physical layer.

2. Answer: D

You can see the current value of the configuration register by using the show version command.
Configuration register is 0x2102

3. Answer: A

 Router#show cdp neighborsCapability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge                  S - Switch, H - Host, I - IGMP, r - Repeater

 4. Answer: B

The IEEE standards relating to Ethernet technology were originally developed for local area networks.
This is the Cisco definition, although in practice this definition is very blurred :-).

 5. Answer: B

The Bridge Priority is the numerical value held by switches. All Catalyst switches have a default priority of 32768. To determine the root bridge you combine the priority of each bridge with its MAC. If two switches have the same priority value the lowest MAC address becomes the root bridge.

6. Answer: D

The Application layer of the OSI model (layer 7) establishes availability of intended communication partners, establishes agreement on procedures regarding error recovery and data integrity and synchronizes networked applications.

7. Answer: C 

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

8. Answer: A

The standard format for printing MAC addresses is six groups of two hexadecimal digits, separated by hyphens (-) or colons (:) e.g. 00-08-74-CE-B7-90, 00:08:74:CE:B7:90.
Another convention commonly used is three groups of four hexadecimal digits separated by dots e.g. 0573.4567.19ab.

How did you go??
I told you they would be random, more coming, stay tuned.

Sunday, March 27, 2016

Cisco CLI Analyzer 2.0 Released - IOS and NX-OS support added!

Cisco CLI Analyzer 2.0
Powered by TAC
What's New?
New name: Now that we support IOS and NX-OS the ASA CLI Analyzer is now the "Cisco CLI Analyzer".
Note: If you currently use Output Interpreter please migrate over to CLI Analyzer as it has more advanced diagnostic capabilities.


  • Advanced System Diagnostics for IOS, IOS-XE, IOS-XR.
  • XR includes "Virtual TAC" providing deep diagnostics and customized analysis.
  • New Contextual Help & Highlighting and System Diagnostic checks added!

Contextual Help & Highlighting
System Diagnostics

  • •Device detection: Information such as serial #, software version, model and device type are automatically added to Cisco supported devices (ASA, IOS*, NX-OS) within the Devices tab.
  • •Contextual Menu: Added the ability to highlight text in the CLI and search
  • Request new CHH content
  • •Keyboard shortcuts: Tab through your sessions (CTRL+Tab), open a new session (ALT+Q) and Search Highlight (CTRL+F)
Save CCO credentials using Master Password.

Overview: In this release of Cisco CLI Analyzer 2.0 we added advanced TAC tools and knowledge to support IOS, IOS-XE, IOS-XR, NX-OS and new ASA content. UCS tools and advanced Case automation capabilities are in the pipeline!
What's next?
 Upgrade to 2.0 now!  The Cisco CLI Analyzer is your ticket to the most current and powerful tools from Cisco TAC.

Free Cisco labs for CCNA, CCNP and CCIE students!
Presented by René Molenaar - CCIE #41726



Monday, March 14, 2016

Networking Questions 2016 - Part 3

The next installment of Six more random networking questions for your enjoyment :-)

1.  When STP is converging no data can move through the switched network.

A) True
B) False

2. What should be carried out within the Cisco hierarchy at the distribution layer?

B) Security and network policies
D) WAN access
E) All of the above

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

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

4. If applied to an interface what would this ACL do?

Router(config)#access-list 25 deny
Router(config)#access-list 25 permit any

A) Deny traffic from the network
B) Deny SMTP traffic from the network
C) Deny traffic from the host
D) Deny SMTP traffic from the host
E) Allow all traffic

5.  Your network features a combination of Cisco, 3COM and Netgear switches. You have been tasked to set up VLANS on your switched network.

What trunking method should you use?

A) Inter-Switch Link
B) IEEE 802.1Q
C) You can't create VLANs by combining switches from different vend

6. When you connect to a remote router "out-of-band", via what port would you connect with?

A) Console port
B) Auxiliary port
C) Ethernet port
D) Serial port

Free Cisco labs for CCNA, CCNP and CCIE students!
Presented by René Molenaar - CCIE #41726

1. Answer A

2. Answer E

Distribution layer (Workgroup layer): Ensures packets are properly routed between subnets and VLANs using LAN-based routers and Layer 3 switches. In the Distribution layer are:
  • Firewalls, security, network policies, and network address translation (NAT) are configured.
  • Routing between workgroups and VLANs is accomplished.
  • Access lists, packet filtering, and queuing are implemented.
3. Answer A

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

4. Answer A

This standard ACL denys traffic from the network and allows everything else.

5. Answer B 

ISL is a Cisco proprietary frame tagging method and therefore only works with Cisco switches.

IEEE 802.1Q is the networking standard that supports virtual LANs (VLANs) on an Ethernet network.

6. Answer B

When a router is out-of-band (out of the network) you would connect remotely via a modem attached to the auxiliary port.

Check back regularly, more questions every week 
(if time permits).

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