Linux, CCNA and MCSE Questions

Friday, August 24, 2007

Hacking Your Password

Hacking Your Password - Password Checking Option and Clearing Chips Password Checking Option
You can use a password during the computer's startup sequence. The options are:

Always, which means every time the system is started.

Setup, which only protects the BIOS routine from being tampered with, or
Disabled.

You can still boot from a floppy and alter things with a diagnostic program, though.The original are: AMI BIOS did not encrypt the password, so any utility capable of reading the CMOS should be able to edit it. The AMI WinBIOS uses a simple substitution system.

You get three attempts to get in, after which the system will have to be rebooted. The default is usually the manufacturer's initials (try ami), or biostar, biosstar, AWARD?SW, AWARD?PW, LKWPETER, 589589, aLLy, condo, djonet, lkwpeter, j262 SWITCHES?SW, AWARD_SW, or Shift + S Y X Z for Award (before 19 Dec 96), but if this doesn't work, or you forget your own password, you must discharge the CMOS. One way to do this is simply to wait for five years until the battery discharges (ten if you've got a Dallas clock chip)! You could also remove the CMOS chip or the battery and just hang on for twenty minutes or so. Look for the chips mentioned below, under Clearing Chips.

You could try flooding the keyboard buffer to crash the password routine -just wait for the password prompt, then keep pressing esc.

Note: Since 19 Dec 96, Award Software has not used a default password, leaving it for OEMs. Discharging the battery will not clear the OEM password.

Note: When CMOS RAM loses power, a bit is set which indicates this to the BIOS during the POST test. As a result, you will normally get slightly more aggressive default values.

If your battery is soldered in, you could discharge it enough so the CMOS loses power, but make sure it is rechargeable so you can get it up to speed again. To discharge it, connect a small resistor (say 39 ohms, or a 6v lantern lamp) across the battery and leave it for about half an hour.

Some motherboards use a jumper for discharging the CMOS; it may be marked CMOS DRAIN. Sometimes, you can connect P15 of the keyboard controller (pin 32, usually) to GND and switch the machine on. This makes the POST run, which deletes the password after one diagnostic test. Then reboot.

Very much a last resort is to get a multi-meter and set it to a low resistance check (i.e. 4 ohms), place one probe on pin 1 of the chip concerned, and draw the other over the other pins. This will shock out the chip and scramble its brains. This is not for the faint hearted, and only for the desperate-use a paperclip or desolder the battery first! We assume no responsibility for damage!

The minimum standby voltage for the 146818 is 2.7v, but your settings can remain even down to around 2.2v. Usually, the clock will stop first, as the oscillator needs a higher voltage to operate. 3v across a CMOS is common with 3.6v nicad & lithium batteries, as the silicon diodes often used in the battery changeover circuit have a voltage drop of 0.6v (3.6v-.6v = 3v). If your CMOS settings get lost when you switch off and the battery is OK, the problem may be in the changeover circuit - the 146818 can be sensitive to small spikes caused by it at power down.

Clearing ChipsThe CMOS can mostly be cleared by shorting together appropriate pins with something like a bent paperclip (with the power off!). You could try a debug script if you are able to boot:
A:\DEBUG- o 70 2E- o 71 FF- q

The CMOS RAM is often incorporated into larger chips:
P82C206 (Square)
Also has 2 DMA controllers, 2 Interrupt controllers, a Timer, and RTC (Real-Time Clock). It's usually marked CHIPS, because it's made by Chips and Technologies. Clear by shorting together pins 12 and 32 on the bottom edge or pins 74 and 75 on the upper left corner.

F82C206 (Rectangular)
Usually marked OPTi (the manufacturer). Has 2 DMA Controllers, 2 Interrupt Controllers, Timer, and Real Time Clock. Clear by shorting pins 3 and 26 on the bottom edge (third pin in from left and 5th pin from right).

Dallas DS1287,DS1287A
Benchmarq bp3287MT, bq3287AMT.
The DS1287 andDS1287A (and compatible Benchmarq bp3287MT and bq3287AMT chips) have a built-in battery, which should last up to 10 years. Clear the 1287A and 3287AMT chips by shorting pins 12 and 21-you cannot clear the 1287 (and 3287MT), so replace them (with a 1287A!). Although these are 24-pin chips, the Dallas chips may be missing 5, which are unused anyway.

Motorola MC146818AP or compatible.
Rectangular 24-pin DIP chip, found on older machines. Compatibles are made by several manufacturers including Hitachi (HD146818AP) and Samsung (KS82C6818A), but the number on the chip should have 6818 in it somewhere. Although pin-compatible with the 1287/1287A, there is no built-in battery, which means it can be cleared by just removing it from the socket, but you can also short pins 12 and 24.

Dallas DS12885S or
Benchmarq bq3258S
Clear by shorting pins 12 and 20, on diagonally opposite corners; lower right and upper left (try also pins 12 and 24).

For reference, the bytes in the CMOS of an AT with ISA bus are arranged thus:

00 Real Time Clock
10-2F ISA Configuration Data
30-3F BIOS-specific information
40-7F Ext CMOS RAM/Advanced Chipset info

The AMI password is in 37h-3Fh, where the (encrypted) password is at 38h-3Fh. If byte 0Dh is set to 0, the BIOS will think the battery is dead and treat what's in the CMOS as invalid.

One other point, if you have a foreign keyboard (that is, outside the United States) - the computer expects to see a USA keyboard until your keyboard driver is loaded, so DON'T use anything in your password that is not in the USA keyboard!

OSI MODEL 7- layers

The OSI (Open System Interconnection) model is developed by ISO in 1984 to provide a reference model for the complex aspects related to network communication. It divides the different functions and services provided by network technology in 7 layers. This facilitates modular engineering, simplifies teaching and learning network technologies, helps to isolate problems, and allows vendors to focus on just the layer(s) in which their hardware or software is implemented and enables them to create products that are compatible, standardized, and interoperable.

APPLICATION (LAYER 7) The Application layer provides network services directly to the user's application such as a web browser or email client. This layer is said to be "closest to the user". Protocols that operate on this layer include TELNET, HTTP, FTP, TFTP, SMTP, and NTP.

PRESENTATION (LAYER 6) The Presentation layer 'represents' the data in a particular format to the Application layer. It defines encryption, compression, conversion and other coding functions. Examples of specifications defined at this layer are GIF, JPEG, MPEG, MIME, and ASCII.

SESSION (LAYER 5) The Session layer establishes, maintains, and terminates end-to-end connections (sessions) between two applications on two network nodes. It controls the dialogue between the source and destination node, which node can send when and for how long. It also provides error reporting for the Application, Presentation and Session layer. Examples of protocols/API's that operate on this layer are RPC and NETBIOS.

TRANSPORT (LAYER 4) The Transport layer converts the data received from the upper layers into segments and prepares them for transport. The Transport layer is responsible for end-to-end (source-to-destination) delivery of entire messages. It allows data to be transferred reliably and uses sequencing to guarantee that it will be delivered in the same order that it was sent. It also provides services such as error checking and flow control (in software). Examples of protocols that operate on this layer are TCP, UDP, NETBEUI, and SPX.The above Transport layer protocols are either connectionless or connection-oriented: Connection-oriented means that a connection (a virtual link) must be established before any actual data can be exchanged. This guarantees that data will arrive, and in the same order as it was sent. It guarantees delivery by sending acknowledgements back to the source when messages are received. TCP is an example of a connection-oriented transport protocol.A common example of connection-oriented communication is a telephone call. You call, the 'destination' picks up the phone and acknowledges, and you start talking (sending data). When a message or a piece of it doesn't arrive, you say: "What!?" and the sender will repeat what he said (retransmit the data).Connectionless is the opposite of connection-oriented; the sender does not establish a connection before it sends data, it just sends it without guaranteeing delivery. UDP is an example of a connectionless transport protocol.

NETWORK (LAYER 3) The Network layer converts the segments from the Transport layer into packets (or datagrams) and is responsible for path determination, routing , and the delivery of packets across internetworks. The network layer treats these packets independently, without recognizing any relationship between those individual packets. It relies on higher layers for reliable delivery and sequencing.The Network layer is also responsible for logical addressing (also known as network addressing or Layer 3 addressing) for example IP addressing. Examples of protocols defined at this layer are IP, IPX, ICMP, RIP, OSPF, and BGP. Examples of devices that operate on this layer are layer-3 switches and routers. The latter includes WAPs with built-in routing capabilities (wireless access routers).

DATA LINK (LAYER 2) The Data Links provides transparent network services to the Network layer so the Network layer can be ignorant about the underlying physical network topology. It is responsible for reassembling bits, taken of the wire by the Physical layer, to frames, and makes sure they are in the correct order and requests retransmission of frames in case an error occurs. It provides error checking by adding a CRC to the frame, and flow control. Examples of devices that operate on this layer are switches, bridges, WAPs, and NICs.

IEEE 802 Data Link sub layersAround the same time the OSI model was developed, the IEEE developed the 802-standards such as 802.5 Token Ring and 802.11 for wireless networks. Both organizations exchanged information during the development, which resulted in two compatible standards. The IEEE 802 standards define physical network components such as cabling and network interfaces, and correspond to the Data Link and/or Physical layer of the OSI model. The IEEE refined the standards and divided the Data Link layer into two sublayers: the LLC and the MAC sublayer.

- LLC sublayerLLC is short for Logical Link Control. The LLC layer is the upper sublayer of the Data Link layer and is defined in the IEEE 802.2 standard. LLC masks the underlying physical network technologies by hiding their differences to provide a single interface to the Network layer. The LLC sublayer uses Source Service Access Points (SSAPs) and Destination Service Access Points (DSAPs) to help the lower layers communicate with the Network layer protocols, acting as an intermediate between the different network protocols (IPX, TCP/IP, etc.) and the different network technologies (Ethernet, Token Ring, etc.). Additionally, this layer is responsible for sequencing and acknowledgements of individual frames.

- MAC sublayerThe Media Access Control layer takes care of physical addressing and allows upper layers access to the physical media, handles frame addressing, error checking. This layer controls and communicates directly with the physical network media through the network interface card. It converts the frames into bits to pass them on to the Physical layer who puts them on the wire (and vice versa). IEEE LAN standards such as 802.3, 802.4, 802.5, and 802.11 define standards for the MAC sublayer as well as the Physical layer.

PHYSICAL (LAYER 1) This layer communicates directly with the physical media. It is responsible for activating, maintaining and deactivating the physical link. It handles a raw bits stream and places it on the wire to be picked up by the Physical layer at the receiving node. It defines electrical and optical signaling, voltage levels, data transmission rates, as well as mechanical specifications such as cable lengths and connectors, the amount of pins and their functions. Examples of devices that operate on this layer are hubs/concentrators, repeaters, NICs, WAPs, and LAN and WAN interfaces such as RS-232, OC-3, BRI, and antennas.

Thursday, August 23, 2007

Active directory collection

Active Directory on a Windows Server 2003 Network
Active Directory is the information hub of the Windows Server 2003 operating system. The following figure shows Active Directory as the focal point of the Windows Server 2003 network used to manage identities and broker relationships between distributed resources so they can work together.

Active Directory provides:
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A central location for network administration and delegation of administrative authority. You have access to objects representing all network users, devices, and resources and the ability to group objects for ease of management and application of security and Group Policy.
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Information security and single sign-on for user access to network resources. Tight integration with security eliminates costly tracking of accounts for authentication and authorization between systems. A single user name and password combination can identify each network user, and this identity follows the user throughout the network.
•
Scalability. Active Directory includes one or more domains, each with one or more domain controllers, enabling you to scale the directory to meet any network requirements.
•
Flexible and global searching. Users and administrators can use desktop tools to search Active Directory. By default, searches are directed to the global catalog, which provides forest-wide search capabilities.
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Storage for application data. Active Directory provides a central location to store data that is shared between applications and with applications that need to distribute their data across entire Windows networks.
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Systematic synchronization of directory updates. Updates are distributed throughout the network through secure and cost-efficient replication between domain controllers.
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Remote administration. You can connect to any domain controller remotely from any Windows-based computer that has administrative tools installed.
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Single, modifiable, and extensible schema. The schema is a set of objects and rules that provide the structure requirements for Active Directory objects. You can modify the schema to implement new types of objects or object properties.
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Integration of object names with Domain Name System (DNS), the Internet-standard computer location system. Active Directory uses DNS to implement an IP-based naming system so that Active Directory services and domain controllers are locatable over standard IP both on intranets and the Internet.
•
Lightweight Directory Access Protocol (LDAP) support. LDAP is the industry standard directory access protocol, making Active Directory widely accessible to management and query applications. Active Directory supports LDAPv3 and LDAPv2.

Seven layers

The specific description for each layer is as follows:
Layer 7: Application Layer
Defines interface to user processes for communication and data transfer in network
Provides standardized services such as virtual terminal, file and job transfer and operations

Layer 6:Presentation Layer
Masks the differences of data formats between dissimilar systems
Specifies architecture-independent data transfer format
Encodes and decodes data; Encrypts and decrypts data; Compresses and decompresses data

Layer 5:Session Layer
Manages user sessions and dialogues
Controls establishment and termination of logic links between users
Reports upper layer errors

Layer 4:Transport Layer
Manages end-to-end message delivery in network
Provides reliable and sequential packet delivery through error recovery and flow control mechanisms
Provides connectionless oriented packet delivery

Layer 3:Network Layer
Determines how data are transferred between network devices
Routes packets according to unique network device addresses
Provides flow and congestion control to prevent network resource depletion

Layer 2:Data Link Layer
Defines procedures for operating the communication links
Frames packets
Detects and corrects packets transmit errors

Layer 1:Physical Layer
Defines physical means of sending data over network devices
Interfaces between network medium and devices
Defines optical, electrical and mechanical characteristics
There are other network architecture models,. Those models will be discussed in separate documents.
The OSI 7 layer model is defined by ISO in document 7498 and ITU X.200, X.207, X.210, X.211, X.212, X.213 , X.214, X.215, X.217 and X.800. The protocols defined by ISO based on the OSI 7 layer mode.

Friday, August 10, 2007

Networking faq

What is ARP?
An:- (Address Resolution Protocol) A TCP/IP protocol for determining the hardware address of a node on a local area network connect to the internet, when only the IP address is know an ARP requests send to the network.

What is BGP?
An: - Border gateway protocol. A protocol used by NSF net that is used on the external gateway protocol.

What is DLC?
An: - Data link control and a error correction protocol in the system network architecture responsible for transmission of data between two nodes are a physical link support windows NT 2000.

What is DBS?
An: - data base administrator the administrator determines the content internal structure and access strategy for a performance.

What is DHCP?
An: - Dynamic host configuration protocol. A TCP/IP protocol that enables a network connected to the internet to assign a Temporary IP address to a host automatically when the host connects to the network.

What is DFS?
An: - Distributed file system. A file management system in which in which file may be located on multiple computers connected over a local or wide area network.

What is DNS?
An: - Domain name system. The hierarchical system by which hosts on the internet have both domain name address (such as vikrantnetworkin.bolgspot.com) and IP address (192.168.1.1). The domain name address is used by human user and automatically translated in to the numerical IP add, which is used by the packet routing software. DNS names consist of a top level domain, a second level domain.

What is FAT?
An: - File allocation table. MS- dos the file allocation table is commonly know as the FAT.

What is HTTP?
An: - Hypertext transfer protocol. The protocol used to carry request from a browser to a web server and to transport pages from web server back to the requesting browser. It is not an especially secure protocol.

What is MS- Dos?
An: - Microsoft disk operating system. A single tasking, single user operating system with a command line interface, released in 1981, for IBM PC and compatibles.
What is NTFS?
An: - New technology file system. An advance file system designed for use specification with the window NT operating system. It supports longs filenames, full security access control, file system recovery, extremely large storage media, and various features for the Windows NT POSIX subsystem. It support always original application by treating all files as object with user defined and system defined attributes.

What is PPP?
An: - Point to point protocol. A widely used data link protocol for transmitting TCP/ IP packets over dialup telephone connection, such as between a computer and the internet. PPP dynamic support of IP add, provides greater protection for data integrity and security and is easier to use than SLIP, at a cost of greater overhead.

What is RAID?
An: - Redundant array or independent disks. A data storage method in which data is distributed across a group of computer disk drives that function as a single storage unit.

What is ICMP?
An: - Internet control message protocol. A network layer internet protocol that provide error correction and other information relevant to IP packet processing for ex. It can let the IP software on one machine inform anther machine about an unreachable destination.

What is IP Sec?
An: - Internet protocol security. A security mechanism under development by the IETF designed to ensure secure packet based on two levels of security.

What is ISP?
An: - Internet service provider. A business that supplies internet connectivity services to individuals, businesses, and other organization. Some ISP is large national or Multinational Corporation that offer access in many locations, while others are limited to single city or region.

What is LAN?
An: - Local area network. A group of computers and other devices dispersed over a relatively limited area and connected by a communication link that enables any device to interact with any other on the network.

What is MAU?
An: - Multi access unit. A hub device in a token ring network that connects computers in a physical hub and spokes arrangement but uses the logical ring required in token ring network.

What is RAM?
An: - Random access memory. A TCP/IP protocol for determining the IP add or a node on a local area network connected to the internet, when only the hardware address is known.

What is SMTP?
An: - Simple mail transfer protocol. A TCP/IP protocol for sending message from one computer to another on a network, this protocol is used on the internet to route e- mail.

What is TCP?
An: - Transmission control protocol. The protocol within TCP/IP that governs the breakup of data message in to packets received by IP a connection oriented reliable protocol.

What is WAN?
An: - Wide Area Network. A geographically widespread network, one that relies on communications capabilities to link the various network segments. A wan can be one large network or it can consist of a number or Linked LAN’s.

Thursday, August 9, 2007

Most popular Demo of networking