Address Resolution Protocol & Display ARP Cache On Computer

Address Resolution Protocol(ARP) finds Physical address(MAC Address) of a network host from IP address of that host. To communicate between two devices, source device must know the IP address and MAC address of the destination device. If the destination device does not have MAC address of the destination device, it sends ARP broadcast to find the MAC address of the network host belongs to the IP address. The device having the IP address(destination device) will respond to the source device with its MAC address. Source device will update ARP cache with the newly find MAC address of the destination device. ARP cache stores MAC address of the other network devices for the future use and periodically undergo flushing to avoid obsolete entries.

How to Display ARP cache On A Computer

To view the MAC address entries stored in ARP(Address Resolution Protocol) cache on your computer, follow the steps below.
  1. Start Command Prompt

  2. Type arp -a to display current ARP entries on your computer
    Table of ARP Cache on My Computer

    PS: arp -g can also be used to display ARP cache on a computer.

On the table, you can find the Physical address of destination devices with IP addresses. Dynamic APR entries are address automatically but the static types are added manually. Static ARP entries remain on ARP cache on your computer until you reboot the system.

ARP Commands
  1. arp -v -This APR command shows current ARP entries in verbose mode.

  2. arp -d - This ARP command can be used to delete a particular ARP entry specified by IP address from ARP cache

  3. arp -s can be used to add a host to APR cache with MAC address and IP address. ARP entries added to ARP cache using this command is permanent and remains until you reboot your computer.

Other Popular Network Protocols

  1. Interior Gateway Routing Protocol (IGRP)

  2. Routing Information Protocol (RIP)

  3. Internet Control Message Protocol (ICMP)

  4. Dynamic Host Configuration Protocol (DHCP)

How to Add a Static Entry in ARP Cache

To add a static entry in ARP cache you can use the command arp -s. The format is provided below.

arp -s 01-00-5e-00-00-16

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Getting Device Manager Error Code 10

If any device connected to your computer is not working properly, first step is to check its status in Device Manager (DM). This tutorial explains device manager error code 10 and the solution to fix it. It tells the device cannot be detected by the computer. Error code 10 comes with following message: This device is either not present, not working properly, or does not have all the drivers installed. (Code 10). Now let us check the normal troubleshooting steps to resolve it.

Standard Procedure to Fix Device Manager Error Code 10
  1. Check Connectivity

    If the hardware not connected properly, you will get this popup. So make sure the unit is connected properly.

  2. Reseat the unit

    It is an extension of first step. You just disconnect the device and reconnect it. Check if the issue persists. This procedure is easy for USB devices because they offer plug and play support. For example if you are using USB wireless adapter to connect your PC to a WiFi network and having the same problem, you may disconnect the adapter from the USB port of your PC and reconnect. After reconnecting the adapter, check for the issue.

  3. Update Driver

    In most cases, outdated driver causes the altert This device is either not present, not working properly, or does not have all the drivers installed. ( 10). Update the current driver installed with latest driver available. You can do it from Device Manager by selecting the hardware which shows issues. To access DM on your computer, follow the instructions provided in the link below.
    How to Access DM

If you are not sure, how to update outdated driver, follow the instructions provided in the link below. You can follow the same method for every hardware units.
How to Update Driver

Just like this issue, another common error is code 1. To learn the reasons and solution to fix that error, visit the link below.
DM Error Code 1

Rarely you may see troubles on your laptop if an adapter is manually disabled. There is a different procedure to handle this situation. To read more about it, visit the link below.
How to Enable WiFi Adapter

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This Device is Not Configured Correctly. (Code 1)

If your computer is unable to configure a device, device manager (DM) will show you error code 1. The complete error code 1 is This device is not configured correctly. (Code 1) To update the drivers for this device, click Update Driver. If that doesn't work, see your hardware documentation for more information. This DM alert is self explanatory. By reading the message itself one can understand the real reason to get this alert. The message also suggests the most effective solution for device manager error code 1.

Solve Error Code 1
  1. Update Driver

    As the warning suggests, the first step to solve error code 1 is to update the driver. To learn how to update driver installed on your PC, click the link below.
    How to update Driver

  2. Remove the Device

    If the updated unit failed to fix the problem, you may want to delete it from Device Manager (DM). After deleting the hardware, you can reconnect it using Add New Hardware Wizard from Control Panel.

If you are still getting error code 1 even after following the both steps, it is the time to check the hardware documentation of the device. Certain devices will not work properly with certain versions of Windows. So you must double check whether the unit you are trying to configure on your computer supports the Operating system and other system settings. If you have migrated from Vista to Windows 8 or 7 recently, there is a chance to see this popup due to the compatibility issues. The hardware unit may not be compatible with latest Operating Systems. Though Windows 8 and 7 has the feature to run a program designed for older versions, rarely incompatible drivers cause issues and warning. You can use "Run this program in compatibility mode for" feature to run the program or hardware unit for current Microsoft OS version.

Further Readings
  1. DM Error PopUp 10

  2. Download Best Free LAN Messenger Tools

  3. How to Download and Create Log Files For IP Messenger Installed

  4. How to Perform Reverse Image Search On Your Computer

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Interior Gateway Routing Protocol (IGRP)

Interior Gateway Routing Protocol (IGRP)

IGRP is an interior gateway protocol

invented by cisco to replace the RIP.

It is a distance-vector routing protocol

used by routers to exchange routing data

within an autonomous system.

Important points
1. IGRP supports multiple metrics for each

route, including bandwidth, delay, load,

MTU, and reliability

2.The maximum hop count of IGRP-routed

packets is 255 (default 100).

1. IGRP is considered a classful routing


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Routing Information Protocol (RIP)

Routing Information Protocol (RIP) - CCNA Tutorials

The Routing Information Protocol (RIP) is a dynamic routing protocol.It is inside the network to create a routing table
which helps routers to understand the layout of the network with changes in network connections. RIP is an interior gateway protocol (IGP) using the distance-vector routing algorithm.

Working of Routing Information Protocol

RIP is a distance-vector routing protocol. It uses hop count as the routing metric. 15 is the maximum number of hops allowed in RIP. RIP sends routing-update messages at regular intervals and when the network topology changes.The normal RIP updation time is 30 seconds while the hold down time is 180 seconds. RIP is based on UDP and working on the Transport layer. Routing by RIP is also called routing by rumor.

RIP Stability Features

RIP implements following mechanisms to maintain the stability. They are:

1. Split horizon
2. Route poisoning
3. Holddown mechanisms

Different versions of RIP

The major versions of Routing Information Protocols are:

1. RIP version 1

2. RIP version 2

3. RIPng

RIP version 1is the basic RIP which doesn't support VLSM. This drawback is fixed on the RIP version 2 where it support Variable Length Subnet Mask (VLSM).RIP version 2 is using multicast where RIP version 1 is using broadcast to send routing updates.RIP version 2 multicasts routing updates to the address is specially defined for IP version 6.

Suggested Readings

1. Interior Gateway Routing Protocol (IGRP)

2. Address Resolution Protocol (ARP)

3. Internet Control Message Protocol (ICMP)

4. Dynamic Host Configuration Protocol (DHCP)

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Practical Uses of Netstat Command in Analyzing Connected Foreign Addresses

Netstat command is a DOS command used to find all active TCP connections between your computer and other network devices with port numbers and TCP connection state. By simply using this command on command prompt, you will get the list of active TCP connections between local IP address(your computer) and foreign IP addresses. You can also find the port numbers open in those connections. With proper syntax we can effectively use it to view how your computer is connected to foreign computers. It has many important uses in computer security. Check the image below to understand its simple use.
proper use

List of Common Netstat Command Syntax
  1. netstat -n : Displays addresses and port numbers in numerical form

  2. netstat -a : Displays all connections and listening ports

  3. netstat -b : Displays the executable involved in creating each connections or listening ports.

  4. netstat -e : Displays Ethernet statistics

  5. netstat -o : Displays the Process Identifier associated with each connection

  6. netstat -p :Shows connections for the specific protocol only

  7. netstat r : Displays the routing table

  8. netstat s : Displays per-protocol statistics

Practical Uses of Netstat Command

If you are working on computer security, it is very handy. There are many practical uses like finding any programs established a connection to Internet without your knowledge, finding the IP address of a chat friend while sharing a file etc. Let us check some of such uses.

  1. Check Programs Established Connections

    It is important to find the names of applications installed on your computer established connection between your computer and a foreign address. Use the following format to find every applications having an active TCP connection.

    netstat -b
    code to find active internet programs

    You must need to run Command Prompt in administrator mode to execute this command. To learn how to do this, visit the link below.
    The Requested Operation Requires Elevation (Run as Administrator)

  2. Find Process Identifiers

    With netstat -o command you can find active TCP connections made on your computer with exact Process Identifiers(PID).
    Practical uses

  3. Find Absolute Domain name of Foreign Host

    One of the important application is to find the absolute domain name or Fully Qualified domain Name(FQDN) of the connected foreign address. It will give you a clear picture of the Internet foreign hosts who are connected to your computer. The syntax to find Fully Qualified domain Name of foreign address is given below.

    netstat -f
    Find FQDN of foreign connections

  4. Find the Offload

    We can find the current offload state of TCP connections using it. The syntax to find current TCP chimney offload state is give below.

    netstat -t
    important uses

Suggested Readings
  1. I Can Ping Global DNS Server Address But Unable To Go Online

  2. How to find the Location of Your Yahoo Messenger Chat Friend

  3. Industry's Best Free Antivirus Software Products

  4. CMD Command To Open DOS In Any Drive

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Tracert- Tool to Find the Path of a Packet

Tracert command is used to determine the path from your computer to destination host by sending ICMP Echo Request messages. The path though which the packet traveled will be printed in the command prompt. ICMP command Tracert is very helpful to troubleshoot any kind of network related issues. It is used to determine the network location where the actual cause of the issue present in any kind of network related issues. It sends ICMP Echo messages to the destination host and decrement its TTL value by one when it pass on hop. When the packets pass each hop it display the path in DOS window and you can easily identify the route. This feature helps to identify the actual cause of any network issue. So it is a handy tool for every network Engineers to analyze and troubleshoot network issues. Let us check how to use this tool.

If you want to know the route of the server of from your computer, you can check it by typing following code on DOS prompt.


We use Tracert command to find out the path taken to deliver the packets to the destination host from the source. Now let us check the general syntax of tracert command.

The general syntax is :
tracert [-d] [-h MaximumHops] [-j HostList] [-w Timeout] [TargetName]

Eg: tracert -h 30 After pressing enter we will a complete trace of the packet sent. The route is expressed in terms of hops. If there is a connection issues, it will show request timed out when the packet reaches the hop which is down.

Related Articles
  1. TTL Expired in Transit

  2. Destination Host Unreachable

  3. Remote Computer Did not Respond

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Create Or Delete Windows User Account From Command Prompt

You can create a user account on your computer directly from Command Prompt by using the DOS command Net User. This command not only helps to create a new user account on a Windows computer but also helps to modify existing user account. This tutorial explains the use of the command net user and explains the procedure to create a new user account on a Windows computer. We also check how to modify an existing user account on a Windows computer using net user command.

Learn The Command Net user

Net user command is used to create, delete and edit user accounts on Windows computers from command prompt. Let us check different syntax to create, modify and delete user accounts from Command Prompt.

  • To create User Account:   net user Username Password /domain

  • To modify User Account:   net user Username Password /add /domain

  • To Delete User Account:   net user Username /delete /domain

While entering username from Command Prompt for a new user account, make sure it is maximum 20 character long. While typing password for the new account, you can use maximum 127 characters.

How to Fetch Admin Account Details From Command Prompt

Another practical use of net user command is to fetch the full information about administrator account on your Windows computer from command prompt. See how I used the net user command to get necessary details about the administrator account from Command Prompt.
Net User command

From this Command Prompt snap, you can see important information like the date on which the user account created, user's country code, the last date on which the password is set and the date on which the current password expires etc. You can also see the last date on which the account is accessed by a user and if there any logon restriction is created, it too will be listed.

Windows Tutorials
  1. How to Unlock Secret Windows Administrator Account

  2. How to use Netstat Command On Your Computer

  3. How to Bypass Windows Admin Account Password

  4. How to Disable USB Ports On a Computer

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Wireless Range Expander- an introduction

The function of a wireless range expanter is to extend the
range of the wireless signal from a wireless router....

The pictorial representation of the working is given below.

Wireless router--------(45 feet)----------------pc

Let us think the range of the router signal is 45 feet.
The wireless adapter on the pc will receive the signal
from the router and will create a connection
between the wireless router and the pc.

If the distance between the pc and wireless router is
70 feet what can we do?

Ans. Establish a range expaner in between the router and the pc.

The range expander will receive signal from the wireless router
and extend the signal to a certain limit.

wireless router-----(40 feet)------range extender----(30 feet)------pc( wireless

Now the wireless computer will go online by receiving signal from range expander.

Detailed explanation will be in the following posts......

Session layer and Its Importance in OSI Reference Model

Session layer is the fifth layer in OSI reference model. It responds to service requests from Presentation layer and issues service requests to Transport layer. The major function of the Session layer is to create, maintain and terminate sessions. Session layer is also responsible for finding and sending data across correct connection. To setup and tear down connection Session layer communicate with Transport layer. Major functions of Session layer are listed below.

The major functions of session layer are:

  1. Starts and ends a session across a network
  2. Allows applications to share information.
  3. Ensures that information is flowing to the right place
  4. Communicate to presentation layer and Transport layer.

We can have multiple sessions on a network due to Session layer.

Eg: We are seeing a movie where sound and the seen both should match. It is one of the application of the Session layer. A list of protocols working in Session layer are listed below.

Major Session layer protocols

  1. AppleTalk Data Stream Protocol (ADSP)
  2. AppleTalk Session Protocol (ASP)
  3. Call Control Protocol for Multimedia Communication
  4. Internet Storage Name Service
  5. Network Basic Input Output (NetBIOS)
  6. Password Authentication Protocol (PAP)
  7. Point-to-Point Tunneling Protocol (PPTP)
  8. Remote Procedure Call Protocol (RPC)
  9. Short Message Peer-to-Peer (SMPP)
  10. Secure Shell (SSH)

Suggested Readings
  1. Physical layer

  2. Data link layer

  3. Network layer

  4. Transport layer

  5. Session layer

  6. Presentation layer

  7. Application layer

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Role of Transport Layer - Responsibilities and Protocols

Transport layer is the fourth layer in OSI Reference Model. It responds to service requests from Session layer and issues service requests to Network layer. Transport Layer is responsible for delivering messages between hosts. In Transport layer, data travels in the form of segments. Transport layer is responsible for creating an end to end connection between source IP and the destination IP. For establishing this end to end connection, Transport layer is using two major protocols TCP and UDP. TCP is connection oriented protocol where UDP is connection less protocol. So by using TCP we can create an end to end reliable connection between source and destination hosts. Transport layer is called host-to-host transport layer in TCP/IP model.

Duties of Transport layer

Major duties of Transport layer are:
  1. Creating an end-to-end connection between hosts in different network,
  2. Error recovery,
  3. Flow control,
  4. Ensuring complete data transfer in TCP
  5. Congestion avoidance

The end to end connection is established in Transport layer with the help of stateful protocol TCP. It offers reliable delivery of data to the destination host. Transport Layer is also responsible for error recovery and is responsible for the resending of data segments which had error. This feature is provided by TCP. Flow control is the process of ensuring where the amount of data sending to the destination is affordable by it. Without flow control a faster source might flood destination with so much information. To accomplish it we are using many techniques like windowing.

Major Transport Layer protocols

1. TCP( Transmission Control Protocol)

2. UDP( User Datagram Protocol)

3. DCCP (Datagram Congestion Control Protocol)

4. SCTP (Stream Control Transmission Protocol).

Suggested Readings
  1. Physical layer

  2. Data link layer

  3. Network layer

  4. Transport layer

  5. Session layer

  6. Presentation layer

  7. Application layer

MAC Sublayer Defined in IEEE 802.3

During the development of IEEE Ethernet, IEEE divided Data Link layer in to two. They are MAC sub layer and LLC sub layer. MAC sublayer functions are performed in hardware and is the bottom part of data link layer. MAC sublayer is defined in IEEE 802.3. MAC sublayer defines how data is transmitted in an Ethernet environment and defines framing, MAC addressing etc. Let us check the functions of MAC sublayer in details below.

Major Functions of MAC Sublayer in IEEE Ethernet
  1. Defines how information is transmitted in an Ethernet environment

  2. MAC Sublayer defines framing

  3. This Sublayer defines the working of Ethernet and MAC addressing

  4. CSMA/CD works in MAC Sublayer

How to Differentiate Ethernet II and MAC Sublayer Frames

We know Ethernet has two versions and it is important to know how to differentiate both versions of Ethernet. Major difference between Ethernet II (developed by DIX) and IEEE 802.2/3 is the frame value. If the frame value is greater than 1500, the frame is of Ethernet II. IEEE version of Ethernet use frames with value less than 1500. DIX version of Ethernet (Ethernet 2) does not have sub layers for data link layer. To read more about LLC Sublayer, visit the link below.
LLC Sublayer (IEEE 802.2 )

Without studying OSI Reference Model, you cannot start computer networking. To read about OSI Reference Model and its seven layered structure, visit the link below.
OSI Reference Model

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LLC (Logical Link Control) IEEE 802.2

In IEEE's version of Ethernet, the top sublayer of Data link layer is Logical Link Control(LLC). LLC's function is performed in software. LLC defines how to multiplex multiple network layer protocols in the data link layer frames. Logical Link Control sublayer performs its multiplexing by using Service Access Point (SAP) identifiers. Logical Link Control sublayer is defined under IEEE 802.2. There are two types of IEEE 802.2 frames. They are:
  1. Service Access Point(SAP)

  2. Subnetwork Access Protocol(SNAP)

Major Duties of Logical Link Control(LLC)
  1. Multiplex multiple network layer protocols in to frames

  2. Sequencing and flow control

IEEE 802.2 uses SAP(Service Access Point) or SNAP(Subnetwork Access Protocol) field to differentiate between encapsulated layer 3 payloads. IEEE 802.2 (LLC) concerns Ethernet, Token Ring and FDDI. To read more about MAC sublayer, visit the link below.
MAC Sublayer IEEE 802.3

Though sequencing and flow control can be done in Logical Link Control Layer, normally this process is done at Transport layer. To read more about different layers in OSI Reference Model, click the link below.
OSI Reference Model

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Data Link Layer Provide Physical Addresses

The second layer in OSI Reference model is Data Link Layer. Data link layer is responsible for providing physical addresses for the devices connected to the network. Physical address is also called hardware address because it is built in address (not a logical address like IP address). Data link layer is responsible for taking bits from Physical layer and convert them to frames. All communications done in Data link layer is in the form of frames.

Sub division in Data-link Layer

In IEEE version of Ethernet, Data link layer is subdivided in to:

1. Logical Link Control (LLC)
2. Media Access Control (MAC)

Data-link Layer devices

Networking devices functioning at Data link layer are:

  1. Switch
  2. NIC
  3. Bridge

Responsibilities of Data Link Layer
  1. Define Physical Addresses
  2. Communication in the same network in form of Frames
  3. Define hardware topology of the network

Major Data Link layer Protocols

  1. CIF : Cells in Frames Ethernet
  2. FDDI : Fiber Distributed Data Interface
  3. GARP : Generic Attribute Registration Protocol
  4. GMRP : Multicast Registration Protocol.
  5. GVRP :GARP VLAN Registration Protocol
  6. LLC :Logical Link Control.
  7. SNAP :SubNetwork Access Protocol

Seven Layer Structure

The seven layer structure of OSI Reference Model is listed below.
  1. Physical layer

  2. Data link layer

  3. Network layer

  4. Transport layer

  5. Session layer

  6. Presentation layer

  7. Application layer

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Physical layer

Physical layer is the first layer in OSI model which deals with the physical transmission medium. The data transferred via physical layer is in the form of electrical signals. In a real life we can treat the physical layer as road where the vehicles are passing.Because the road is the one which is carrying the vehicles and linking the cities. Like that the physical layer is transmitting the data signal in the form of electrical signal and connecting nodes.

The major cables using in physical layer are:

1. Coaxial cable

2. Twisted pair cable

3. Optical fiber cable

Devices working in physical layer:

1. Internet gateway

2. Hub

3. Repeater

The major functions and services performed by the Physical Layer are:

1. Bit-by-bit delivery

2. Modulation

3. Encoding and Signaling:

4. Bit synchronization

5. Physical network Topology

In Physical Layer data is transmitting in the form of electric pulse and the cables are responsible for the safe delivery of the signals. Physical Layer is also responsible for varying the wave form for the ease of data transfer. This process is know as modulation. Physical layer is also responsible for various types of encoding and decoding of signals.Physical layer also caring the transmission mode and physical lay out of the network( topology)

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OSI Reference Model

The International Organization for Standardization (ISO) developed a seven layer model called Open Systems Interconnection (OSI)Reference Model to help vendors and network experts to learn how data is transferred between networking devices. OSI Reference Model helps networking device manufactures to implement new network standards and policies. OSI Reference Model helps network administrators to reduce the complexity of networks and makes it easy to troubleshoot networking issues.

Seven Layers of OSI Reference Model

There are seven layers in OSI Reference Model and each layer has specific role in data communication. Seven layers of OSI reference model are listed below.

  1. Physical layer

  2. Data link layer

  3. Network layer

  4. Transport layer

  5. Session layer

  6. Presentation layer

  7. Application layer

What is The Need of OSI Reference Model

Prior to the introduction of Open System Interconnection (OSI) Reference Model, each vendors have their own manufacturing standards. It forced the user to stuck with single vendor for all his/her networking needs because devices from different vendors were not compatible. To overcome this issue International Organization for Standardization (ISO) introduced the seven layer OSI architecture. OSI Reference Model tells how to connect two layers in networks and helped vendors to make products in universal standards.

Benefits of OSI Reference Model

The major benefits of OSI Reference Model in a computer network are listed below.
  1. OSI Reference Model promotes interoperability between vendors by defining the process of connecting two layers.

  2. By dividing a network in to layers, we split complex network activities in to a set of simple components.

  3. Helps vendors to follow modular design

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Effective Use of Ping Utility

Ping is a network utility to check the connectivity between two nodes in a computer network. Ping sends ICMP packets to destination device and if the packets reach the destination successfully, source device will receive ICMP replies. If the ICMP packets failed to reach the destination, we will get ping packet loss reply. ICMP is the short form of Internet Control Message Protocol. To check the connectivity of a destination host, say a website, follow the instructions.
  1. Open Command Prompt

  2. type ping [Destination Address] and press enter.

    Eg: ping
    Ping command to check connectivity

Practical Uses of Ping Command
  1. How to Change Default TTL Value Set On  Packets

  2.  Transmit failed. General Failure

  3. Automatically Set Continuous Echo Requests To a Destination Until We Manually Stop

  4. How to Change Default Size of ICMP Echo Request On Your Computer(ping -l)

  5. How to Check Optimium MTU Size Value Of Your Network

  6. Packet Needs To Be Fragmented But DF Set -Reason and Solution

  7. Tell Packets to Don't Fragment While in Test

How Ping Operates

It is important to learn the operation of ping utility. When we ping a destination host from our computer, ping sends ICMP echo request packets to the destination. Normally ping sends four packets and then wait for the ICMP reply from the destination host. If the packets reach the destination host successfully, our computer will receive ICMP reply from the destination. If there is no valid ICMP reply from the destination, ping displays packet loss message.

Possible Replies You Get When Ping a Destination Host

Based on the status of ICMP echo packets send, we may get different types of ICMP replies.
  1.  Reply: Destination Host Unreachable

  2.  Packets Error: Destination Net Unreachable

  3. ICMP Reply: Request Timed Out

  4. ICMP Echo Gives Hardware Error

  5. Request Could not Find Host. Please Check the Name and Try again

  6. Transmission Failed Error Code 31

  7. Error 628: The Connection was Terminated by the Remote computer before it could be Completed

  8. Error 797: A Connection to the Remote Access Server was not Made because the Modem was not Found

  9. Error 769: The Specified Destination is not Reachable

  10. The Requested Operation Requires Elevation

  11. Either you Specified a Destination Address that is not Valid or Remote Server is Down

Malicious uses of Ping Utility

Ping utility is used to find if a particular host is accessible or running. The same utility can be used to prevent a destination host from working smoothly. Here I give a list of tutorials tell the malicious use of ping utility to disturb the normal operations of devices connected to the Internet.
  1. Denial of Service (DOS) attacks

  2. How to Conduct Smurf Attack

  3. How to Perform TCP Split Handshake Attack

  4. Guide to DDOS Attack

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