Free E-book

CISCO

2008-07-31T11:57:00.002+07:00

Corporate history

Len Bosack and Sandy Lerner, a married couple that worked in computer operations staff at Stanford University, later joined by Richard Troiano, founded Cisco Systems in 1984. The name "Cisco" was derived from the city name, San Francisco. Bosack adapted multiple-protocol router software originally written by William Yeager, another staff employee who had begun the work years before Bosack arrived from the University of Pennsylvania, where Bosack had received his bachelor's degree.

While Cisco was not the first company to develop and sell a router (a device that forwards computer traffic between two or more networks), it was one of the first to sell commercially successful routers supporting multiple network protocols. As the Internet Protocol (IP) has become a standard, the importance of multi-protocol routing as a function has declined. Today, Cisco's largest routers are marketed to route primarily IP packets and MPLS frames.

In 1990, the company went public and was listed on the Nasdaq stock exchange. Lerner was fired and because of that, Bosack quit but not before receiving $200 million. Most of those profits were given to charities and the two later divorced.

During the Internet boom in 1999, the company acquired Cerent Corp., a start-up company located in Petaluma, California, for about US$7 billion. It was the most expensive acquisition made by Cisco at that time. Since then, only Cisco's acquisition of Scientific-Atlanta has been bigger.

In late March 2000, at the height of the dot-com boom, Cisco was the most valuable company in the world, with a market capitalization of more than US$500 billion. In 2007, with a market cap of about US$180 billion, it is still one of the most valuable companies.

Cisco has made inroads into many network equipment markets outside routing, including Ethernet switching, remote access, branch office routers, ATM networking, security, IP telephony, and others. In 2003, Cisco acquired Linksys, a popular manufacturer of computer networking hardware and positioned it as a leading brand for the home and end user networking market (SOHO). More recently, on July 23, 2008 Cisco acquired leading home network management software company Pure Networks, creator of Network Magic; thus, opening new doors as the leader in a growing software and hardware networking industry -- Cisco leading the way.

The company was a 2002-03 recipient of the Ron Brown Award.

Cisco has put a major effort into its foray into virtualization technologies. Announced in early 2008, with broad facing concept to a self healing system capable of 15 terabits per second transfer rates. The new type of NX-OS based operating system fully virtualized with tool sets to apply programmable APIs with web services oriented tool sets to control the switch with XML applying them across contexts automatically. Security with link layer based encryption embedded into the switching the fabric itself with tags applied independent to IP addresses creating a fully abstracted set of ACLs to control while staying separate from machine addresses in a typical network installation.

USB

2008-07-31T00:18:00.000+07:00

In information technology, Universal Serial Bus (USB) is a serial bus standard to interface devices. USB was designed to allow many peripherals to be connected using a single standardized interface socket and to improve the plug-and-play capabilities by allowing devices to be connected and disconnected without rebooting the computer (hot swapping). Other convenient features include providing power to low-consumption devices without the need for an external power supply and allowing many devices to be used without requiring manufacturer specific, individual device drivers to be installed.

USB is intended to help retire all legacy varieties of serial and parallel ports. USB can connect computer peripherals such as computer mouse, keyboards, PDAs, gamepads and joysticks, scanners, digital cameras, printers, personal media players, and flash drives. For many of those devices USB has become the standard connection method. USB was originally designed for personal computers, but it has become commonplace on other devices such as PDAs and video game consoles. As of 2008, there are about 2 billion USB devices in the world.^[1]

The design of USB is standardized by the USB Implementers Forum (USB-IF), an industry standards body incorporating leading companies from the computer and electronics industries. Notable members have included Agere (now merged with LSI Corporation), Apple Inc., Hewlett-Packard, Intel, NEC, and Microsoft.

DTMF

2008-07-31T00:11:00.001+07:00

Dual-tone multi-frequency (DTMF) signaling is used for telephone signaling over the line in the voice-frequency band to the call switching center. The version of DTMF used for telephone tone dialing is known by the trademarked term Touch-Tone (canceled March 13, 1984), and is standardized by ITU-T Recommendation Q.23. Other multi-frequency systems are used for signaling internal to the telephone network.

As a method of in-band signaling, DTMF tones were also used by cable television broadcasters to indicate the start and stop times of local commercial insertion points during station breaks for the benefit of cable companies. Until better out-of-band signaling equipment was developed in the 1990s, fast, unacknowledged, and loud DTMF tone sequences could be heard during the commercial breaks of cable channels in the United States and elsewhere.

History

In the time preceding the development of DTMF, telephone systems employed a system commonly referred to as pulse (Dial Pulse or DP in the U.S.) or loop disconnect (LD) signaling to dial numbers, which functions by rapidly disconnecting and connecting the calling party's telephone line, similar to flicking a light switch on and off. The repeated connection and disconnection, as the dial spins, sounds like a series of clicks. The exchange equipment counts those clicks or dial pulses to determine the called number. Loop disconnect range was restricted by telegraphic distortion and other technical problems, and placing calls over longer distances required either operator assistance (operators used an earlier kind of multi-frequency dial) or the provision of subscriber trunk dialing equipment.

Dual Tone Multi-Frequency, or DTMF, is a method for instructing a telephone switching system of the telephone number to be dialed, or to issue commands to switching systems or related telephony equipment.

The DTMF dialing system traces its roots to a technique developed by Bell Labs in the 1950s called MF (Multi-Frequency) which was deployed within the AT&T telephone network to direct calls between switching facilities using in-band signaling. In the early 1960s, a derivative technique was offered by AT&T through its Bell System telephone companies as a "modern" way for network customers to place calls. In AT&Ts Compatibility Bulletin No. 105, AT&T described the product as "a method for pushbutton signaling from customer stations using the voice transmission path."

The consumer product was marketed by AT&T under the registered trade name Touch-Tone. Other vendors of compatible telephone equipment called this same system "Tone" dialing or "DTMF," or used their own registered trade names such as the "Digitone" of Northern Electric.

The DTMF system uses eight different frequency signals transmitted in pairs to represent sixteen different numbers, symbols and letters - as detailed below.

ICMP

2008-07-28T01:02:00.000+07:00

The Internet Control Message Protocol (ICMP) is one of the core protocols of the Internet protocol suite. It is chiefly used by networked computers' operating systems to send error messages—indicating, for instance, that a requested service is not available or that a host or router could not be reached.

ICMP ^[1] relies on IP to perform its tasks, and it is an integral part of IP. It differs in purpose from transport protocols such as TCP and UDP in that it is typically not used to send and receive data between end systems. It is usually not used directly by user network applications, with some notable exceptions being the ping tool and traceroute.

Technical details

Internet control message protocol is part of the Internet protocol suite as defined in RFC 792. ICMP messages are typically generated in response to errors in IP datagrams (as specified in RFC 1122) or for diagnostic or routing purposes.

The version of ICMP for Internet Protocol version 4 is also known as ICMPv4, as it is part of IPv4. IPv6 has an equivalent protocol, ICMPv6.

ICMP messages are constructed at the IP layer, usually from a normal IP datagram that has generated an ICMP response. IP encapsulates the appropriate ICMP message with a new IP header (to get the ICMP message back to the original sending host) and transmits the resulting datagram in the usual manner.

For example, every machine (such as intermediate routers) that forwards an IP datagram has to decrement the time to live (TTL) field of the IP header by one; if the TTL reaches 0, an ICMP Time to live exceeded in transit message is sent to the source of the datagram.

Each ICMP message is encapsulated directly within a single IP datagram, and thus, like UDP, ICMP is unreliable.

Although ICMP messages are contained within standard IP datagrams, ICMP messages are usually processed as a special case, distinguished from normal IP processing, rather than processed as a normal sub-protocol of IP. In many cases, it is necessary to inspect the contents of the ICMP message and deliver the appropriate error message to the application that generated the original IP packet, the one that prompted the sending of the ICMP message.

Many commonly-used network utilities are based on ICMP messages. The traceroute command is implemented by transmitting UDP datagrams with specially set IP TTL header fields, and looking for ICMP Time to live exceeded in transit (above) and "Destination unreachable" messages generated in response. The related ping utility is implemented using the ICMP "Echo request" and "Echo reply" messages.

UDP

2008-07-28T01:01:00.000+07:00

User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. Using UDP, programs on networked computers can send short messages sometimes known as datagrams (using Datagram Sockets) to one another. UDP is sometimes called the Universal Datagram Protocol. The protocol was designed by David P. Reed in 1980 and formally defined in RFC 768.

UDP does not guarantee reliability or ordering in the way that TCP does. Datagrams may arrive out of order, appear duplicated, or go missing without notice. Avoiding the overhead of checking whether every packet actually arrived makes UDP faster and more efficient, for applications that do not need guaranteed delivery. Time-sensitive applications often use UDP because dropped packets are preferable to delayed packets. UDP's stateless nature is also useful for servers that answer small queries from huge numbers of clients. Unlike TCP, UDP is compatible with packet broadcast (sending to all on local network) and multicasting (send to all subscribers).

Common network applications that use UDP include: the Domain Name System (DNS), streaming media applications such as IPTV, Voice over IP (VoIP), Trivial File Transfer Protocol (TFTP) and online games.

Ports

Main article: List of TCP and UDP port numbers

UDP uses ports to allow application-to-application communication. The port field is a 16 bit value, allowing for port numbers to range between 0 and 65,535. Port 0 is reserved, but is a permissible source port value if the sending process does not expect messages in response.

Ports 1 through 1023 (hex 3FF) are named "well-known" ports and on Unix-derived operating systems, binding to one of these ports requires root access.

Ports 1024 through 49,151 (hex BFFF) are registered ports.

Ports 49,152 through 65,535 (hex FFFF) are used as temporary ports primarily by clients when communicating to servers.

Bridges

2008-07-27T01:30:00.001+07:00

Bridges

Main article: Network bridge

A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges do not promiscuously copy traffic to all ports, as hubs do, but learns which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address only to that port. Bridges do send broadcasts to all ports except the one on which the broadcast was received.

Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived.

Bridges come in three basic types:

Local bridges: Directly connect local area networks (LANs)
Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced by routers.
Wireless bridges: Can be used to join LANs or connect remote stations to LANs

Computer Network

2008-07-27T01:05:00.001+07:00

A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and presents the basic components of a network.

Network Classification

The following list presents major categories used for classifying networks.

Scale

Computer networks may be classified according to the scale: Personal area network (PAN), Local Area Network (LAN), Campus Area Network (CAN), Metropolitan area network (MAN), or Wide area network (WAN). Also a business area network

As Ethernet increasingly is the standard interface for networks, these distinctions are more important to the network administrator than the user. Network administrators may have to tune the network, to correct delay issues and achieve the desired performance level.

Connection method

Computer networks can also be classified according to the hardware technology that is used to connect the individual devices in the network such as Optical fibre, Ethernet, Wireless LAN, HomePNA, or Power line communication.

Ethernets use physical wiring to connect devices. Often they employ hubs, switches, bridges, and/or routers.

Wireless LAN technology is built to connect devices without wiring. These devices use a radio frequency to connect.

Functional relationship (Network Architectures)

Computer networks may be classified according to the functional relationships which exist between the elements of the network, e.g., Active Networking, Client-server and Peer-to-peer (workgroup) architecture.

Cisco Configuration

2008-07-26T15:07:00.002+07:00

1. Getting started with Cisco

Initially you will probably configure your router from a terminal. If the router is already configured and at least one port is configured with an IP address, and it has a physical connection to the network, you might be able to telnet to the router and configure it across the network. If it is not already configured, then you will have to directly connect to it with a terminal and a serial cable. With any Windows box you can use Hyperterminal to easily connect to the router. Plug a serial cable into a serial (COM) port on the PC and the other end into the console port on the Cisco router. Start Hyperterminal, tell it which COM port to use and click OK. Set the speed of the connection to 9600 baud and click OK. If the router is not on, turn it on.

If you wish to configure the router from a Linux box, either Seyon or Minicom should work. At least one of them, and maybe both, will come with your Linux distribution.

Often you will need to hit the Enter key to see the prompt from the router. If it is unconfigured it will look like this:

Router>

If it has been previously configured with a hostname, it will look like this:

hostname of router>

If you have just turned on the router, after it boots it will ask you if you wish to begin initial configuration. Say no. If you say yes, it will put you in the menu interface. Say no.

1.1 Modes

The Cisco IOS command-line interface is organized around the idea of modes. You move in and out of several different modes while configuring a router, and which mode you are in determines what commands you can use. Each mode has a set of commands available in that mode, and some of these commands are only available in that mode. In any mode, typing a question mark will display a list of the commands available in that mode.

Router>?

1.2 Unprivileged and privileged modes

When you first connect to the router and provide the password (if necessary), you enter EXEC mode, the first mode in which you can issue commands from the command-line. From here you can use such unprivileged commands as ping, telnet, and rlogin. You can also use some of the show commands to obtain information about the system. In unprivileged mode you use commands like, show version to display the version of the IOS the router is running. Typing show ? will diplay all the show commands available in the mode you are presently in.

Router>show ?

You must enter privileged mode to configure the router. You do this by using the command enable. Privileged mode will usually be password protected unless the router is unconfigured. You have the option of not password protecting privileged mode, but it is HIGHLY recommended that you do. When you issue the command enable and provide the password, you will enter privileged mode.

To help the user keep track of what mode they are in, the command-line prompt changes each time you enter a different mode. When you switch from unprivileged mode to privileged mode, the prompt changes from:

Router>

Router#

This would probably not be a big deal if there were just two modes. There are, in fact, numerous modes, and this feature is probably indispensable. Pay close attention to the prompt at all times.

Within privileged mode there are many sub-modes. In this document I do not closely follow Cisco terminology for this hierarchy of modes. I think that my explanation is clearer, frankly. Cisco describes two modes, unprivileged and privileged, and then a hierarchy of commands used in privileged mode. I reason that it is much clearer to understand if you just consider there to be many sub-modes of privileged mode, which I will also call parent mode. Once you enter privileged mode (parent mode) the prompt ends with a pound sign (#). There are numerous modes you can enter only after entering privileged mode. Each of these modes has a prompt of the form:

Router(arguments)#

They still all end with the pound sign. They are subsumed within privileged mode. Many of these modes have sub-modes of their own. Once you enter priliged mode, you have access to all the configuration information and options the IOS provides, either directly from the parent mode, or from one of its submodes.

2. Configuring your Cisco Router

If you have just turned on the router, it will be completely unconfigured. If it is already configured, you may want to view its current configuration. Even if it has not been previously configured, you should familiarize yourself with the show commands before beginning to configure the router. Enter privileged mode by issuing the command enable, then issue several show commands to see what they display. Remember, the command show ? will display all the showcommands aavailable in the current mode. Definately try out the following commands:

   Router#show interfaces
  Router#show ip protocols
  Router#show ip route
  Router#show ip arp

When you enter privileged mode by using the command enable, you are in the top-level mode of privileged mode, also known in this document as "parent mode." It is in this top-level or parent mode that you can display most of the information about the router. As you now know, you do this with the show commands. Here you can learn the configuration of interfaces and whether they are up or down. You can display what IP protocols are in use, such as dynamic routing protocols. You can view the route and ARP tables, and these are just a few of the more important options.

As you configure the router, you will enter various sub-modes to set options, then return to the parent mode to display the results of your commands. You also return to the parent mode to enter other sub-modes. To return to the parent mode, you hit ctrl-z. This puts any commands you have just issued into affect, and returns you to parent mode.

2.1 Global configuration (config)

To configure any feature of the router, you must enter configuration mode. This is the first sub-mode of the parent mode. In the parent mode, you issue the command config.

   Router#config
  Router(config)#

As demonstrated above, the prompt changes to indicate the mode that you are now in.

In connfiguration mode you can set options that apply system-wide, also refered to as "global configurations." For instance, it is a good idea to name your router so that you can easily identify it. You do this in configuration mode with the hostname command.

   Router(config)#hostname ExampleName
  ExampleName(config)#

As demonstrated above, when you set the name of the host with the hostname command, the prompt immediately changes by replacing Router with ExampleName. (Note: It is a good idea to name your routers with an organized naming scheme.)

Another useful command issued from config mode is the command to designate the DNS server to be used by the router:

   ExampleName(config)#ip name-server aa.bb.cc.dd
  ExampleName(config)#ctrl-Z
  ExampleName#

This is also where you set the password for privileged mode.

   ExampleName(config)#enable secret examplepassword
  ExampleName(config)#ctrl-Z
  ExampleName#

Until you hit ctrl-Z (or type exit until you reach parent mode) your command has not been put into affect. You can enter config mode, issue several different commands, then hit ctrl-Z to activate them all. Each time you hit ctrl-Z you return to parent mode and the prompt:

ExampleName#

Here you use show commands to verify the results of the commands you issued in config mode. To verify the results of the ip name-server command, issue the command show host.

2.2 Configuring Cisco router interfaces

Cisco interface naming is straightforward. Individual interfaces are referred to by this convention:

media type slot#/port#

"Media type" refers to the type of media that the port is an interface for, such as Ethernet, Token Ring, FDDI, serial, etc. Slot numbers are only applicable for routers that provide slots into which you can install modules. These modules contain several ports for a given media. The 7200 series is an example. These modules are even hot-swapable. You can remove a module from a slot and replace it with a different module, without interrupting service provided by the other modules installed in the router. These slots are numbered on the router.

Port number refers to the port in reference to the other ports in that module. Numbering is left-to-right, and all numbering starts at 0, not at one.

For example, a Cisco 7206 is a 7200 series router with six slots. To refer to an interface that is the third port of an Ethernet module installed in the sixth slot, it would be interface ethernet 6/2. Therefor, to display the configuration of that interface you use the command:

ExampleName#show interface ethernet 6/2

If your router does not have slots, like a 1600, then the interface name consists only of:

media type port#

For example:

ExampleName#show interface serial 0

Here is an example of configuring a serial port with an IP address:

   ExampleName#config
  ExampleName(config)#interface serial 1/1
  ExampleName(config-if)#ip address 192.168.155.2 255.255.255.0
  ExampleName(config-if)#no shutdown
  ExampleName(config-if)#ctrl-Z
  ExampleName#

Then to verify configuration:

ExampleName#show interface serial 1/1

Note the no shutdown command. An interface may be correctly configured and physically connected, yet be "administratively down." In this state it will not function. The command for causing an interface to be administratively down is shutdown.

   ExampleName(config)#interface serial 1/1
  ExampleName(config-if)#shutdown
  ExampleName(config-if)#ctrl-Z
  ExampleName#show interface serial 1/1

In the Cisco IOS, the way to reverse or delete the results of any command is to simply put no infront of it. For instance, if we wanted to unassign the IP address we had assigned to interface serial 1/1:

   ExampleName(config)#interface serail 1/1
  ExampleName(config-if)#no ip address 192.168.155.2 255.255.255.0
  ExampleName(config-if)ctrl-Z
  ExampleName#show interface serial 1/1

Configuring most interfaces for LAN connections might consist only of assigning a network layer address and making sure the interface is not administratively shutdown. It is usually not necessary to stipulate data-link layer encapsulation. Note that it is often necessary to stipulate the appropriate data-link layer encapsulation for WAN connections, such as frame-relay and ATM. Serial interfaces default to using HDLC. A discussion of data-link protocols is outside the scope of this document. You will need to look up the IOS command encapsulation for more details.

2.3 Configuring Cisco Routing

IP routing is automatically enabled on Cisco routers. If it has been previously disabled on your router, you turn it back on in config mode with the command ip routing.

   ExampleName(config)#ip routing
  ExampleName(config)#ctrl-Z

There are two main ways a router knows where to send packets. The administrator can assign static routes, or the router can learn routes by employing a dynamic routing protocol.

These days static routes are generally used in very simple networks or in particular cases that necessitate their use. To create a static route, the administrator tells the router operating system that any network traffic destined for a specified network layer address should be forwarded to a similiarly specified network layer address. In the Cisco IOS this is done with the ip route command.

   ExampleName#config
  ExampleName(config)#ip route 172.16.0.0 255.255.255.0 192.168.150.1
  ExampleName(config)#ctrl-Z
  ExampleName#show ip route

Two things to be said about this example. First, the packet destination address must include the subnet mask for that destination network. Second, the address it is to be forwarded to is the specified addres of the next router along the path to the destination. This is the most common way of setting up a static route, and the only one this document covers. Be aware, however, that there are other methods.

Dynamic routing protocols, running on connected routers, enable those routers to share routing information. This enables routers to learn the routes available to them. The advantage of this method is that routers are able to adjust to changes in network topologies. If a route is physically removed, or a neighbor router goes down, the routing protocol searches for a new route. Routing protocols can even dynamically choose between possible routes based on variables such as network congestion or network reliability.

There are many different routing protocols, and they all use different variables, known as "metrics," to decide upon appropriate routes. Unfortunately, a router needs to be running the same routing protocols as its neighbors. Many routers can, however, run mutliple protocols. Also, many protocols are designed to be able to pass routing information to other routing protocols. This is called "redistribution." The author has no experience with trying to make redistribution work. There is an IOS redistribute command you can research if you think this is something you need. This document's compagnion case study describes an alternative method to deal with different routing protocols in some circumstances.

Routing protocols are a complex topic and this document contains only this superficial description of them. There is much to learn about them, and there are many sources of information about them available. An excelent source of information on this topic is Cisco's website, http://www.cisco.com.

This document describes how to configure the Routing Information Protocol (RIP) on Cisco routers. From the command-line, we must explicitly tell the router which protocol to use, and what networks the protocol will route for.

   ExampleName#config
  ExampleName(config)#router rip
  ExampleName(config-router)#network aa.bb.cc.dd
  ExampleName(config-router)#network ee.ff.gg.hh
  ExampleName(config-router)#ctrl-Z
  ExampleName#show ip protocols

Now when you issue the show ip protocols command, you should see an entry describing RIP configuration.

2.4 Saving your Cisco Router configuration

Once you have configured routing on the router, and you have configured individual interfaces, your router should be capable of routing traffic. Give it a few moments to talk to its neighbors, then issue the commands show ip route and show ip arp. There should now be entries in these tables learned from the routing protocol.

If you turned the router off right now, and turned it on again, you would have to start configuration over again. Your running configuration is not saved to any perminent storage media. You can see this configuration with the command show running-config.

ExampleName#show running-config

You do want to save your successful running configuration. Issue the command copy running-config startup-config.

ExampleName#copy running-config startup-config

Your configuration is now saved to non-volatile RAM (NVRAM). Issue the command show startup-config.

ExampleName#show startup-config

Now any time you need to return your router to that configuration, issue the command copy startup-config running-config.

ExampleName#copy startup-config running-config

2.5 Example Cisco Router configuration

Router>enable
Router#config
Router(config)#hostname N115-7206
N115-7206(config)#interface serial 1/1
N115-7206(config-if)ip address 192.168.155.2 255.255.255.0
N115-7206(config-if)no shutdown
N115-7206(config-if)ctrl-z
N115-7206#show interface serial 1/1
N115-7206#config
N115-7206(config)#interface ethernet 2/3
N115-7206(config-if)#ip address 192.168.150.90 255.255.255.0
N115-7206(config-if)#no shutdown
N115-7206(config-if)#ctrl-z
N115-7206#show interface ethernet 2/3
N115-7206#config
N115-7206(config)#router rip
N115-7206(config-router)#network 192.168.155.0
N115-7206(config-router)#network 192.168.150.0
N115-7206(config-router)#ctrl-z
N115-7206#show ip protocols
N115-7206#ping 192.168.150.1
N115-7206#config
N115-7206(config)#ip name-server 172.16.0.10
N115-7206(config)#ctrl-z
N115-7206#ping archie.au
N115-7206#config
N115-7206(config)#enable secret password
N115-7206(config)#ctrl-z
N115-7206#copy running-config startup-config
N115-7206#exit

3. Troubleshooting your Cisco router

Inevitably, there will be problems. Usually, it will come in the form of a user notifying you that they can not reach a certain destination, or any destinattion at all. You will need to be able to check how the router is attempting to route traffic, and you must be able to track down the point of failure.

You are already familiar with the show commands, both specific commands and how to learn what other show commands are available. Some of the most basic, most useful commands you will use for troubleshooting are:

   ExampleName#show interfaces
  ExampleName#show ip protocols
  ExampleName#show ip route
  ExampleName#show ip arp

WEP

2008-07-23T17:43:00.001+07:00

Wired Equivalent Privacy

Wired Equivalent Privacy (WEP) is a deprecated algorithm to secure IEEE 802.11 wireless networks. Wireless networks broadcast messages using radio and are thus more susceptible to eavesdropping than wired networks. When introduced in 1999, WEP was intended to provide confidentiality comparable to that of a traditional wired network.

Beginning in 2001, several serious weaknesses were identified by cryptanalysts with the result that today a WEP connection can be cracked with readily available software within minutes.^[1] Within a few months the IEEE created a new 802.11i task force to counteract the problems. By 2003, the Wi-Fi Alliance announced that WEP had been superseded by Wi-Fi Protected Access (WPA), which was a subset of then upcoming 802.11i amendment. Finally in 2004, with the ratification of the full 802.11i standard (a.k.a. WPA2), the IEEE declared that both WEP-40 and WEP-104 "have been deprecated as they fail to meet their security goals".^[2] Despite its weaknesses, WEP is still widely in use.^[3] WEP is often the first security choice presented to users by router configuration tools even though it provides a level of security that deters only unintentional use, leaving the network vulnerable to deliberate compromise.^[4]

WEP is sometimes inaccurately referred to as Wireless Encryption Protocol.

Authentication

Two methods of authentication can be used with WEP: Open System authentication and Shared Key authentication.

For the sake of clarity, we discuss WEP authentication in the Infrastructure mode (ie, between a WLAN client and an Access Point), but the discussion applies to the Ad-Hoc mode too.

In Open System authentication, the WLAN client need not provide its credentials to the Access Point during authentication. Thus, any client, regardless of its WEP keys, can authenticate itself with the Access Point and then attempt to associate. In effect, no authentication (in the true sense of the term) occurs. After the authentication and association, WEP can be used for encrypting the data frames. At this point, the client needs to have the right keys.

In Shared Key authentication, WEP is used for authentication. A four-way challenge-response handshake is used:

I) The client station sends an authentication request to the Access Point.

II) The Access Point sends back a clear-text challenge.

III) The client has to encrypt the challenge text using the configured WEP key, and send it back in another authentication request.

IV) The Access Point decrypts the material, and compares it with the clear-text it had sent. Depending on the success of this comparison, the Access Point sends back a positive or negative response. After the authentication and association, WEP can be used for encrypting the data frames.

At first glance, it might seem as though Shared Key authentication is more secure than Open System authentication, since the latter offers no real authentication. However, it is quite the reverse. It is possible to derive the static WEP key by capturing the four handshake frames in Shared Key authentication.^[1] Hence, it is advisable to use Open System authentication for WEP authentication, rather than Shared Key authentication. (Note that both authentication mechanisms are weak).

SSID

2008-07-23T17:34:00.002+07:00

A service set identifier, or SSID, is a name used to identify the particular 802.11 wireless LANs to which a user wants to attach. A client device will receive broadcast messages from all access points within range advertising their SSIDs, and can choose one to connect to based on pre-configuration, or by displaying a list of SSIDs in range and asking the user to select one.

Description

It is normal for multiple access points to share the same SSID if they provide access to the same network.

In 802.11 it is possible to create an ad-hoc network of client devices (an IBSS), in which case the SSID is chosen by the client device that starts the network, and broadcasting of the SSID is performed in a pseudo-random order by all devices that are members of the network.

As the SSID is a name that may be displayed to users, it normally consists of displayable ASCII characters. However the standard does not require this—the SSID is defined as a sequence of 1–32 octets each of which may take any value.

Some wireless access points support broadcasting multiple SSIDs, allowing the creation of Virtual Access Points—partitioning a single physical access point into several logical access points, each of which can have a different set of security and network settings.

SSID Client Isolation prohibits wireless clients in the same subnet from communicating directly with each other and thereby bypassing the firewall

Not broadcasting the SSID

Some people have erroneously attempted to improve security by turning off the broadcast of the SSID.^[1] To a user, depending on the wireless software, the network either does not show up, or is displayed as "Unnamed Network". In any case, one needs to manually enter the correct SSID to connect to the network.

This method is not secure, because every time someone connects to the network, the SSID is transmitted in cleartext even if the wireless connection is otherwise encrypted. An eavesdropper can passively sniff the wireless traffic on that network undetected (with software like Kismet), and wait for someone to connect, revealing the SSID. Sometimes, in large networks there is even frequent enough connection requests to see the name listed without additional software. Alternatively, there are faster (albeit detectable) methods where a cracker spoofs a "disassociate frame" as if it came from the wireless router, and sends it to one of the clients connected; the client will immediately re-connect, revealing the SSID.

Thus, this should not be used to protect a wireless network against determined crackers.^[2] Other forms of authentication should be used, of which WEP is the most universal but still easily broken. The best security encryption is WPA(2).

[edit] Basic service set identifier

A related field is the BSSID or Basic Service Set Identifier, which uniquely identifies each BSS (the SSID however, can be used in multiple, possibly overlapping, BSSs). In an infrastructure BSS, the BSSID is the MAC address of the wireless access point (AP). In an independent (ad-hoc) basic service set, the BSSID is a locally administered MAC address generated from a 46-bit random number. The individual/group bit of the address is set to 0. The universal/local bit of the address is set to 1.

A BSSID with a value of all 1s is used to indicate the broadcast BSSID. A broadcast BSSID may only be used during probe requests.

WIBro

2008-07-22T16:39:00.001+07:00

WiBro (Wireless Broadband) is a wireless broadband Internet technology being developed by the South Korean telecoms industry. WiBro is the South Korean service name for IEEE 802.16e (mobile WiMAX) international standard.

WiBro adapts TDD for duplexing, OFDMA for multiple access and 8.75 MHz as a channel bandwidth. WiBro was devised to overcome the data rate limitation of mobile phones (for example CDMA 1x) and to add mobility to broadband Internet access (for example ADSL or Wireless LAN). In February 2002, the Korean government allocated 100 MHz of electromagnetic spectrum in the 2.3 - 2.4 GHz band, and in late 2004 WiBro Phase 1 was standardized by the TTA of Korea and in late 2005 ITU reflected WiBro as IEEE 802.16e (mobile WiMAX). Two South Korean Telco (KT, SKT) launched commercial service in June 2006, and the tariff is around US$30.

WiBro base stations will offer an aggregate data throughput of 30 to 50 Mbit/s and cover a radius of 1-5 km allowing for the use of portable internet usage. In detail, it will provide mobility for moving devices up to 120 km/h (74.5 miles/h) compared to Wireless LAN having mobility up to walking speed and Mobile Phone having mobility up to 250 km/h. From testing during the APEC Summit in Busan in late 2005, the actual range and bandwidth were quite a bit lower than these numbers. The technology will also offer Quality of Service. The inclusion of QoS allows for WiBro to stream video content and other loss-sensitive data in a reliable manner. These all appear to be (and may be) the stronger advantages over the fixed WiMAX standard (802.16a). Some Telcos in many countries are trying to commercialize this Mobile WiMAX (or WiBro). For example, TI (Italia), TVA (Brazil), Omnivision (Venezuela), PORTUS (Croatia), and Arialink (Michigan) will provide commercial service after test service around 2006-2007. While WiBro is quite exacting in its requirements from spectrum use to equipment design, WiMAX leaves much of this up to the equipment provider while providing enough detail to ensure interoperability between designs.

WDS

2008-07-22T16:38:00.001+07:00

A Wireless Distribution System is a system that enables the wireless interconnection of access points in an IEEE 802.11 network. It allows a wireless network to be expanded using multiple access points without the need for a wired backbone to link them, as is traditionally required. The notable advantage of WDS over other solutions is that it preserves the MAC addresses of client packets across links between access points. ^[1]

An access point can be either a main, relay or remote base station. A main base station is typically connected to the wired Ethernet. A relay base station relays data between remote base stations, wireless clients or other relay stations to either a main or another relay base station. A remote base station accepts connections from wireless clients and passes them to relay or main stations. Connections between "clients" are made using MAC addresses rather than by specifying IP assignments.

All base stations in a Wireless Distribution System must be configured to use the same radio channel, and share WEP keys or WPA keys if they are used. They can be configured to different service set identifiers. WDS also requires that every base station be configured to forward to others in the system.

WDS may also be referred to as repeater mode because it appears to bridge and accept wireless clients at the same time (unlike traditional bridging). It should be noted, however, that throughput in this method is halved for all clients connected to a router that is connected with WDS.

Google Hacking

2008-07-16T20:27:00.002+07:00

Have you ever had a hobby that changed your life? This Google Hacking thing
began as a hobby, but sometime in 2004 it transformed into an unexpected gift. In that
year, the high point of my professional career was a speaking gig I landed at Defcon. I
was on top of the world that year and I let it get to my head—I really was an egotistical
little turd. I presented my Google Hacking talk, making sure to emulate the rockstar
speakers I admired.The talk went well, securing rave reviews and hinting at a
rock-star speaking career of my own.The outlook was very promising, but the
weekend left me feeling empty.
In the span of two days a series of unfortunate events flung me from the mountaintop
of success and slammed me mercilessly onto the craggy rocks of the valley of
despair. Overdone? A bit, but that’s how it felt for me—and I didn’t even get a Balroc
carcass out of the deal. I’m not sure what caused me to do it, but I threw up my hands
and gave up all my professional spoils—my career, my five hundred user website and
my fledgling speaking career—to God.
At the time, I didn’t exactly understand what that meant, but I was serious about
the need for drastic change and the inexplicable desire to live with a higher purpose.
For the first time in my life, I saw the shallowness and self-centeredness of my life, and
it horrified me. I wanted something more, and I asked for it in a real way.The funny
thing is, I got so much more than I asked for.
Syngress approached and asked if I would write a book on Google Hacking, the first
edition of the book you’re holding. Desperately hoping I could mask my inexperience
and distaste for writing, I accepted what I would come to call the “original gift.”
Google Hacking is now a best seller.
My website grew from 500 to nearly 80,000 users.The Google book project led to
ten or so additional book projects.The media tidal wave was impressive—first came
Slashdot, followed quickly by the online, print,TV and cable outlets. I quickly earned
my world traveler credentials as conference bookings started pouring in.The community
I wanted so much to be a part of—the hacking community—embraced me
unconditionally, despite my newly conservative outlook.They bought books through
my website, generating income for charity, and eventually they fully funded my wife
and me on our mission’s trip to Uganda, Africa.That series of events changed my life
and set the stage for ihackcharities.com, an organization aimed at connecting the skills
of the hacking community with charities that need those skills. My “real” life is transformed
as well—my relationship with my wife and kids is better than it ever has been.
So as you can see, this is so much more than just a book to me.This really was
the original gift, and I took the task of updating it very seriously. I’ve personally
scrutinized every single word and photo—especially the ones I’ve written—to make
sure it’s done right. I’m proud of this second edition, and I’m grateful to you, the
reader, for supporting the efforts of the many that have poured themselves into this
project.Thank you.
Thank you for visiting us at http://johnny.ihackstuff.com and for getting the
word out.Thank you for supporting and linking to the Google Hacking Database.
Thank you for clicking through our Amazon links to fund charities. Thank you for
giving us a platform to affect real change, not only in the security community but also
in the world at large. I am truly humbled by your support.

by
Johnny. I Hack Stuff

Download here

Free C Language ebook

2008-07-10T21:00:00.001+07:00

The C programming language was originally developed by Dennis Ritchie of Bell Laboratories,
and was designed to run on a PDP-11 with a UNIX operating system. Although it was originally
intended to run under UNIX, there was a great interest in running it on the IBM PC and compatibles,
and other systems. C is excellent for actually writing system level programs, and the
entire Applix 1616/OS operating system is written in C (except for a few assembler routines).
It is an excellent language for this environment because of the simplicity of expression, the
compactness of the code, and the wide range of applicability.
It is not a good "beginning" language because it is somewhat cryptic in nature. It allows the
programmer a wide range of operations from high level down to a very low level approaching
the level of assembly language. There seems to be no limit to the flexibility available. One
experienced C programmer made the statement, "You can program anything in C", and the
statement is well supported by my own experience with the language. Along with the resulting
freedom however, you take on a great deal of responsibility. It is very easy to write a program
that destroys itself due to the silly little errors that, say, a Pascal compiler will flag and call a
fatal error. In C, you are very much on your own, as you will soon find.
Since C is not a beginners language, I will assume you are not a beginning programmer, and I
will not attempt to bore you by defining a constant and a variable. You will be expected to
know these basic concepts. You will, however, not be expected to know anything of the C
programming language. I will begin with the highest level of C programming, including the
usually intimidating concepts of pointers, structures, and dynamic allocation. To fully understand
these concepts, it will take a good bit of time and work on your part, because they not
particularly easy to grasp, but they are very powerful tools. Enough said about that, you will
see their power when we get there, just don't allow yourself to worry about them yet.
Programming in C is a tremendous asset in those areas where you may want to use Assembly
Language, but would rather keep it a simple to write and easy to maintain program. It has been
said that a program written in C will pay a premium of a 50 to 100% increase in runtime, because
no language is as compact or fast as Assembly Language. However, the time saved in coding
can be tremendous, making it the most desirable language for many programming chores. In
addition, since most programs spend 90 percent of their operating time in only 10 percent or
less of the code, it is possible to write a program in C, then rewrite a small portion of the code
in Assembly Language and approach the execution speed of the same program if it were written
entirely in Assembly Language.
Approximately 75 percent of all new commercial programs introduced for the IBM PC have
been written in C, and the percentage is probably growing. Apple Macintosh system software
was formerly written in Pascal, but is now almost always written in C. The entire Applix 1616
operating system is written in C, with some assembler routines.
Since C was designed essentially by one person, and not by a committee, it is a very usable
language but not too closely defined. There was no official standard for the C language, but the
American National Standards Association (ANSI) has developed a standard for the language,
so it will follow rigid rules. It is interesting to note, however, that even though it did not have
a standard, the differences between implementations are usually small. This is probably due to
the fact that the original unofficial definition was so well thought out and carefully planned that
extensions to the language are not needed.

Get Download pdf File