You have a private or public network with servers and workstations that are assigned static and dynamic IP addresses (either private or public IPs). You assigned them the static IP addresses due to NAT (Network Address Translation) or for public access, and dynamic IP addresses via the DHCP. Even if you kept a good record of those assigned IPs, there are times when you want to find all IP addresses of networked devices. The following procedure may be used to determine IP addresses of networked devices that are connected to your network.

RJ-45 conductor data cable contains 4 pairs of wires each consists of a solid colored wire and a strip of the same color. There are two wiring standards for RJ-45 wiring: T-568A and T-568B. Although there are 4 pairs of wires, 10BaseT/100BaseT Ethernet uses only 2 pairs: Orange and Green. The other two colors (blue and brown) may be used for a second Ethernet line or for phone connections. The two wiring standards are used to create a cross-over cable (T-568A on one end, and T-568B on the other end), or a straight-through cable (T-568B or T-568A on both ends).

Denial of service attacks are major nuisance for web hosts, and as a web host you'll have to take every measure to protect your resources from DoS attacks. Our APF, BFD, DDoS and RootKitarticle describes Linux utilities available to protect from DDoS attack, and also explains installation procedures. This article supplements above article by providing means to control traffic (bandwidth shaping) with Linux "tc" command so that no single machine can waste the entire network bandwidth.

IP Spoofing is a technique used to gain unauthorized access to machines, whereby an attacker illicitly impersonates another machine by manipulating IP packets. IP Spoofing involves modifying the packet header with a forged (spoofed) source IP address, a checksum, and the order value. Internet is a packet switched network, which causes the packets leaving one machine may be arriving at the destination machine in different order. The receiving machine resembles the message based on the order value embedded in the IP header. IP spoofing involves solving the algorithm that is used to select the order sent values, and to modify them correctly.

Ipconfig is a MS-DOS command-line tool used to display and manage the network settings of your computer. Ipconfig is available on Windows machines, and it displays the current network connection details and DHCP client settings.

The Dynamic Host Configuration Protocol (DHCP) is a network protocol that functions at the application layer of the Internet Protocol (IP) suite. A server that uses DHCP will be able to dynamically assign IP Addresses and other network configuration parameters to devices on the network; thus, allowing communication to a second network. The protocol can be implemented in networks of any size, ranging from small home area networks (HANs) to large campus area networks (CANs) and even the networks used by Internet Service Providers (ISPs).

TCP/IP, Transmission ControlProtocol/Internet Protocol, is the suite of two protocols, TCP and IP, used to interconnect network devices on the Internet. The TCP performs the handshake between the network devices to establish a socket. The socket remains open during the communication. The source TCP converts the data into packets and sends them to the destination TCP. The TCP performs acknowledgment for the successful delivery of the packets. If a packet drops on the way, the source TCP resends the packet. The IP layer is responsible for sending and receiving the data to the correct destination. The TCP/IP stack is comprised of the following layers.

MAC, Media Access Control, address is a globally unique identifier assigned to network devices, and therefore it is often referred to as hardware or physical address. MAC addresses are 6-byte (48-bits) in length, and are written in MM:MM:MM:SS:SS:SS format. The first 3-bytes are the ID number of the manufacturer, which is assigned by an Internet standards body. The second 3-bytes are serial numbers assigned by the manufacturer.