There are a couple of ways to create subnets. In this article we will subnet a class C address 192.168.0.0 that, by default, has 24 subnet bits and 8 host bits. Before we start subnetting, we have to ask ourselves these two questions: 1. How many subnets do we need? 2x = number of subnets. x is the number of 1s in the subnet …
CIDR (Classless inter-domain routing) is a method of public IP address assignment. It was introduced in 1993 by Internet Engineering Task Force with the following goals: to deal with the IPv4 address exhaustion problem to slow down the growth of routing tables on Internet routers Before CIDR, public IP addresses were assigned based on the …
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ping is perhaps the most commonly used tool to troubleshoot a network. Ping (Packet Internet Groper) is included with most operating systems. It is invoked using a ping command and uses ICMP (Internet Control Message Protocol) to reports errors and provides information related to IP packet processing. Ping works by sending an ICMP echo request message to the specified IP …
Traceroute is a command-line interface based tool used to identify the path used by a packet to reach its target. This tool also uses ICMP messages, but unlike ping, it identifies every router in a path taken by the packets. Traceroute is useful when troubleshooting network problems because it can help identify where exactly the problem …
The TCP/IP suite is a set of protocols used on computer networks today (most notably on the Internet). It provides an end-to-end connectivity by specifying how data should be packetized, addressed, transmitted, routed and received on a TCP/IP network. This functionality is organized into four abstraction layers and each protocol in the suite resides in …
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One of the main protocols in the TCP/IP suite is the Transmission Control Protocol (TCP). TCP provides reliable and ordered delivery of data between applications running on hosts on a TCP/IP network. Because of its reliable nature, TCP is used by applications that require high reliability, such as FTP, SSH, SMTP, HTTP, etc. TCP is connection-oriented, …
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One other important protocol in the TCP/IP site is User Datagram Protocol (UDP). This protocol is basically a scaled-down version of TCP. Just like TCP, this protocol provides delivery of data between applications running on hosts on a TCP/IP network, but, unlike TCP, it does not sequence the data and does not care about the order …
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A port is a 16-bit number used to identify specific applications and services. TCP and UDP specify the source and destination port numbers in their packet headers and that information, along with the source and destination IP addresses and the transport protocol (TCP or UDP), enables applications running on hosts on a TCP/IP network to communicate. Applications …
ARP (Address Resolution Protocol) is a network protocol used to find out the hardware (MAC) address of a device from an IP address. It is used when a device wants to communicate with some other device on a local network (for example on an Ethernet network that requires physical addresses to be known before sending packets). …
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DHCP (Dynamic Host Configuration Protocol) DHCP is a network protocol that is used to assign various network parameters to a device. This greatly simplifies the administration of a network, since there is no need to assign static network parameters for each device. DHCP is a client-server protocol. A client is a device that is configured …
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Telnet is a network protocol that allows a user to communicate with a remote device. It is a virtual terminal protocol used mostly by network administrators to remotely access and manage devices. The administrator can access the device by telnetting to the IP address or hostname of a remote device. To use telnet, you must have …
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FTP (File Transfer Protocol) FTP is a network protocol used to transfer files from one computer to another over a TCP network. Like Telnet, it uses a client-network architecture, which means that a user has to have an FTP client installed to access the FTP server running on a remote machine. After establishing the FTP …
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Simple Network Management Protocol (SNMP) is an application layer protocol that is used for network device management. This protocol can collects and manipulate valuable network information from switches, routers, servers, printers, and other network-attached devices. An SNMP-managed network consists of two components: Network management station (NMS) – the software which runs on the administrative computer. This software …
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HTTP (Hypertext Transfer Protocol) HTTP is a client-server protocol that allows clients to request web pages from web servers. It is an application level protocol widely used on the Internet. Clients are usually web browsers. When a user wants to access a web page, a browser sends an HTTP Request message to the web server. …
Network Time Protocol (NTP) is an application layer protocol used for clock synchronization between hosts on a TCP/IP network. The goal of NTP is to ensure that all computers on a network agree on the time, since even a small difference can create problems. For example, if there is more than 5 minutes difference on your …
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Automatic Private IP Addressing (APIPA) is a feature in operating systems (such as Windows) that enables computers to automatically self-configure an IP address and subnet mask when their DHCP server isn’t reachable. The IP address range for APIPA is 169.254.0.1-169.254.255.254, with the subnet mask of 255.255.0.0. When a DHCP client boots up, it looks for a DHCP server …
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ICMP (Internet Control Message Protocol) is a network layer protocol that reports errors and provides information related to IP packet processing. ICMP is used by network devices to send error messages indicating, for example, that a requested service is not available or that a host isn’t reachable. ICMP is commonly used by network tools such as ping or traceroute. …
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An IP header is a prefix to an IP packet that contains information about the IP version, length of the packet, source and destination IP addresses, etc. It consists of the following fields: Here is a description of each field: Version – the version of the IP protocol. For IPv4, this field has a value of 4. Header …
IOS (Internetwork Operating System) is a multitasking operating system used on most Cisco routers and switches. IOS has a command-line interface with the predetermined number of multiple-word commands. This operating system is used to configure routing, switching, internetworking and other features supported by a Cisco device. NOTE Previous versions of Cisco switches ran CatOS, a discounted …
When you first power on a newly purchased Cisco device, it will perform a power-on-self-test (POST) to discover the hardware components and verify that all components work properly. If the POST is successful, the device will enter the setup mode. This mode presents a step-by-step dialog to help you configure some basic parameters, such as the device …