Open Shortest Path First (OSPF) uses which type of algorithm for its routing protocol?

Open Shortest Path First (OSPF) uses which type of algorithm for its routing protocol?

• Distance-vector
• Unidirectional link detection
• Frame-relay
• Link-state 

EXPLANATION

 Open Shortest Path First (OSPF) is a link-state routing protocol, rather than a distance vector protocol. The main difference here is that a linked-state protocol does not send its routing table in the form of updates, but only shared its connectivity configuration. By collecting connectivity information from all of the devices on the network, OSPF can store all this information in a database and use that information to build a topology map.

This information will allow OSPF to identify the best or shortest route to every other network segment on the network. The route selection is based on overall hops to the destination, as well as link speed or link cost.

The topology not only includes the best route to the destination as calculated by the Dijkstra algorithm (a search algorithm created by Edsger Dijkstra), but also, when possible, it includes a candidate or backup route to the destination.

After creating the topology map, OSPF populates the routing table with the chosen routes to each destination. As traffic passes from router to router, each router evaluates the best path to the destination network. In some cases, this process can lead to routing loops on the network, because each one is evaluating the path based on its own link state database.

The OSPF interior network protocol belongs to a single routing domain (or group of routers) known as an Autonomous System (AS). All routers belonging to the same AS share connection information and build their linked-state database from that information.

Specifically with OSPF, as opposed to link-state terminology in general, the primary, or best, route the destination goes through is the Designated Router (DR), although if it fails, the secondary or backup path will be sent to the Backup Designated Router (BDR).

OSPF typically uses multicast to share connection information with its neighbors, and this information is sent to the 224.0.0.5 multicast address.

OSPF is an open protocol and is defined in RFC2328 for version 2 of the protocol. Version 3 of OSPF has been updated to support IPv6 and is defined in RFC5340. Other than for the newly integrated support for IPv6, no major technical differences exist between version 2 and version 3.

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In Windows, how do you configure the firewall to allow pings?

In Windows, how do you configure the firewall to allow pings?

• File and Printer Sharing
• Netlogon Service
• HomeGroup In
• Key Management Service 

EXPLANATION

1. Search for Windows Firewall, and click to open it.
   Note:

   For help navigating, see Get around in Windows.
2. Click Advanced Settings on the left.
3. From the left pane of the resulting window, click Inbound Rules.
4. In the right pane, find the rules titled File and Printer Sharing (Echo Request - ICMPv4-In).
5. Right-click each rule and choose Enable Rule.

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The first modems used a set of command codes to operate. What two letters did these generally start with, and what did it stand for?

The first modems used a set of command codes to operate. What two letters did these generally start with, and what did it stand for?

• AT - Automated Telephony
• AD - Access Dialling
• AT - Attention
• AD - Automated Dialling 

EXPLANATION

AT commands are instructions used to control a modem. AT is the abbreviation of ATtention. Every command line starts with "AT" or "at". That's why modem commands are called AT commands. Many of the commands that are used to control wired dial-up modems, such as ATD (Dial), ATA (Answer), ATH (Hook control) and ATO (Return to online data state), are also supported by GSM/GPRS modems and mobile phones. Besides this common AT command set, GSM/GPRS modems and mobile phones support an AT command set that is specific to the GSM technology, which includes SMS-related commands like AT+CMGS (Send SMS message), AT+CMSS (Send SMS message from storage), AT+CMGL (List SMS messages) and AT+CMGR (Read SMS messages).
Note that the starting "AT" is the prefix that informs the modem about the start of a command line. It is not part of the AT command name. For example, D is the actual AT command name in ATD and +CMGS is the actual AT command name in AT+CMGS. However, some books and web sites use them interchangeably as the name of an AT command.
Here are some of the tasks that can be done using AT commands with a GSM/GPRS modem or mobile phone:

• Get basic information about the mobile phone or GSM/GPRS modem. For example, name of manufacturer (AT+CGMI), model number (AT+CGMM), IMEI number (International Mobile Equipment Identity) (AT+CGSN) and software version (AT+CGMR).
  
• Get basic information about the subscriber. For example, MSISDN (AT+CNUM) and IMSI number (International Mobile Subscriber Identity) (AT+CIMI).
  
• Get the current status of the mobile phone or GSM/GPRS modem. For example, mobile phone activity status (AT+CPAS), mobile network registration status (AT+CREG), radio signal strength (AT+CSQ), battery charge level and battery charging status (AT+CBC).
  
• Establish a data connection or voice connection to a remote modem (ATD, ATA, etc).
  
• Send and receive fax (ATD, ATA, AT+F*).
  
• Send (AT+CMGS, AT+CMSS), read (AT+CMGR, AT+CMGL), write (AT+CMGW) or delete (AT+CMGD) SMS messages and obtain notifications of newly received SMS messages (AT+CNMI).
  
• Read (AT+CPBR), write (AT+CPBW) or search (AT+CPBF) phonebook entries.
  
• Perform security-related tasks, such as opening or closing facility locks (AT+CLCK), checking whether a facility is locked (AT+CLCK) and changing passwords (AT+CPWD).
  (Facility lock examples: SIM lock [a password must be given to the SIM card every time the mobile phone is switched on] and PH-SIM lock [a certain SIM card is associated with the mobile phone. To use other SIM cards with the mobile phone, a password must be entered.])
  
• Control the presentation of result codes / error messages of AT commands. For example, you can control whether to enable certain error messages (AT+CMEE) and whether error messages should be displayed in numeric format or verbose format (AT+CMEE=1 or AT+CMEE=2).
  
• Get or change the configurations of the mobile phone or GSM/GPRS modem. For example, change the GSM network (AT+COPS), bearer service type (AT+CBST), radio link protocol parameters (AT+CRLP), SMS center address (AT+CSCA) and storage of SMS messages (AT+CPMS).
  
• Save and restore configurations of the mobile phone or GSM/GPRS modem. For example, save (AT+CSAS) and restore (AT+CRES) settings related to SMS messaging such as the SMS center address.
  

Note that mobile phone manufacturers usually do not implement all AT commands, command parameters and parameter values in their mobile phones. Also, the behavior of the implemented AT commands may be different from that defined in the standard. In general, GSM/GPRS modems designed for wireless applications have better support of AT commands than ordinary mobile phones.
In addition, some AT commands require the support of mobile network operators. For example, SMS over GPRS can be enabled on some GPRS mobile phones and GPRS modems with the +CGSMS command (command name in text: Select Service for MO SMS Messages). But if the mobile network operator does not support the transmission of SMS over GPRS, you cannot use this feature.

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How many addresses are in the range 192.168.0.1/32?

How many addresses are in the range 192.168.0.1/32?

• 255
• 32
• 1
• 1024 

EXPLANATION

IP Address: 192.168.0.1 Network Address: 192.168.0.1 Usable Host IP Range: NA Broadcast Address: 192.168.0.1 Total Number of Hosts: 1 Number of Usable Hosts: 0 Subnet Mask: 255.255.255.255 Wildcard Mask: 0.0.0.0 Binary Subnet Mask: 11111111.11111111.11111111.11111111 IP Class: C CIDR Notation: /32 IP Type: Private Short: 192.168.0.1 /32 Binary ID: 11000000101010000000000000000001 Integer ID: 3232235521 Hex ID: 0xc0a80001 in-addr.arpa: 1.0.168.192.in-addr.arpa

SOURCE

https://subnet.techlanda.com/

 

 

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In Microsoft .Net, the value of VBNULL is

In Microsoft .Net, the value of VBNULL is

• 0
• 1
• Nothing
• -1 

EXPLANATION

Indicates that the type of a variant object is Nothing. Returned by the VarType function.

C#

public const Microsoft.VisualBasic.VariantType vbNull = 1;

vbNull is a Long with a value of 1. It is probably the most misunderstood constant in all of Visual Basic. It is a variable type constant like vbEmpty (0), vbInteger (2), vbLong (3) etc 

 

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Which PowerShell command helps you search for cmdlets currently available to you?

Which PowerShell command helps you search for cmdlets currently available to you?

• All-Commands
• Get-Command
• Search-Command
• Find-Command 

EXPLANATION

The PowerShell Get-Command cmdlet (‘command let’) in my opinion is the first PowerShell command you should know – that is if you are new to PowerShell.
PowerShell Get-Command lists all available PowerShell Cmdlets, Functions and Modules in your computer. I guess you are already beginning to see how helpful PowerShell Get-Command can be.
This is why I said that the Get-Command is a Cmdlet you need to know. The reason is simple. If you need a Cmdlet but you don’t know the Cmdlet or you cannot remember it, PowerShell Get-Command will help you find it.

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Which of the following is not considered an input device for a computer?

Which of the following is not considered an input device for a computer?

• USB hub
• Keyboard
• Mouse
• MFP printer 

EXPLANATION

In computing, a printer is a peripheral device which makes a persistent representation of graphics or text, usually on paper.
While most output is human-readable, bar code printers are an example of an expanded use for printers. The different types of printers include 3D printer, inkjet printer, laser printer, thermal printer, etc.

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