List kept by routers to control access to or from the router for a number of services.
Short for Address Resolution Protocol. ARP is an internet protocol used to map an IP address to a MAC address. ARP is a required TCP/IP standard defined in RFC 826.
Refers to the speed at which a communication system can transfer data, usually measured in bits per second.
Refers to the delay in transmission of data through the circuits of a computer's microprocess or or over a TCP/IP network. The delay typically occurs when a system's bandwidth cannot support the amount of information being relayed at the speed it is being processed. There are, however, many factors that can create a bottleneck in a system. Bottlenecks affect network performance by slowing down the flow of information transmitted across networks. TCP/IP connections were originally designed to transmit only text files, and the proliferation of bandwidth-intensive transmissions such as high-resolution graphics has caused bottlenecks in the process; therefore, the data moves more slowly across networks.
Short for Bits Per Second. In data communications, bits per second (abbreviated bps) is a common measure of data speed for computer modem and transmission carriers. As the term implies, the speed in bps is equal to the number of bits transmitted or received each second.
A common address that is used to direct (broadcast) a message to all terminals in a network
An undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and, typically, causes network time-outs. Broadcast storms can usually be prevented by carefully configuring a network to block illegal broadcast messages
A storage area used for handling data in transit. Buffers are used in internetworking to compensate for differences in processing speed between network devices. Bursts of data can be stored in buffers until they can be handled by slower processing devices.Buffer is also referred to as a packet buffer.
A unit of data that is eight binary digits long. A byte is the unit most computers use to represent a character such as a letter, number, or typographic symbol(for example, \"g\", \"5\", or \"?\")
Short for Cisco Discovery Protocol. CDP is a media- and protocol-independent device-discovery protocol that runs on all Cisco-manufactured equipment including routers, access servers, bridges, and switches. Using CDP, a device can advertise its existence to other devices and receive information about other devices on the same LAN or on the remote side of a WAN. The devices do not need to have any network layer protocols configured in order to use CDP, although if these addresses are configured CDP will discover them. Each device configured for CDP sends out periodic messages to a MAC layer multicast address. These advertisements include information about the capabilities and software version of the advertising platform. This gives you an easy way to see other Cisco devices on your network without having to figure out which devices are Cisco by the vendor code embedded in the Media Access Control address.
The authentication string used to communicate with the SNMP agent running on a device
All Cisco Router have a 16-bit configuration register, which is stored in a special memory location in NVRAM. This register controls a number of function.
Short for Dynamic Host Control Protocol. An effective way to dynamically assign and reuse a fixed number of IP addresses when there are more devices on the network than addresses available. A DHCP server dynamically assigns IP addresses to devices requesting them. These address assignments expire after a time specified by the network manager.The DHCP server then reassigns these addresses to other devices as needed. DHCP is an extension to BOOTP in which the address assignments are static.
Number of packets discarded either due to their error content or free up buffer space.
Short for Domain Name System (or Service). The Domain Name System (DNS) is a distributed Internet directory service. DNS is used mostly to translate between domain names and IP addresses. Most Internet services rely on DNS to work, and if DNS fails, websites cannot be located and email delivery stalls.
A server that runs DNS server programs containing name-to-IP address mappings, IP address-to-name mappings, information about the domain tree structure,and other information. DNS servers also attempt to resolve client queries. The DNS system consists of three components: DNS data (called resource records),servers (called name servers) and Internet protocols for fetching data from the servers.
A portion of memory, usually a variable, which has a length of four bytes. The term dword is given to anything which is four bytes in length. Literally, a dword is a\"double word.\"For example for the IP Address 206.191.158.55, enter the following keystrokes into the calculator exactly as shown: 206 * 256 + 191 = * 256 + 158 = * 256 + 55 =The dword equivalent of the IP address will be the result. In this case, 3468664375.
Number of inbound packets that could not be transmitted to a higher layer protocol because of their error content.
A special type of EEPROM (electrically erasable programmable read-only memory) that can be erased and reprogrammed in blocks instead of one byte at a time. Many modernPCs have their BIOS stored on a Flash memory chip so that it can be updated easily if necessary. Such a BIOS is sometimes called a flash BIOS. Flash memory is also popular in modems because it enables the modem manufacturer to support new protocols as they become standardized.
Forward DNS (domain name system) Lookup uses an Internet domain name to find an IPaddress. When you enter the address for a Web site at your browser, the address is transmitted to a nearby router which does a forward DNS lookup in a routing table to locate the IP address. Forward DNS lookup is the more common lookup since most users think in terms of domain names rather than IP addresses.
Refers to the number of packets that are discarded by the router because they exceed the medium's maximum packet size.
A major numbering system used by computers is hexadecimal or Base 16. In this system, the numbers are counted from 0 to 9 then letters A to F before adding another digit.The letter A through F represent decimal numbers 10 through 15 respectively.
Refers to the order in which the TCP/IP packets progress from machine to machine, called the 'distance' (in hops) from the originating machine.
A fully qualified domain name (usually alphabetic) identifying the address of one specific host computer on the Internet. The host address is a subset of the IP address.
Short for Internet Control Message Protocol. ICMP is an extension to the InternetProtocol (IP) defined by RFC 792. ICMP supports packets containing error, control,and informational messages. The PING command, for example, uses ICMP to test an Internet connection.
The number of inbound packets which were chosen to be discarded even though no errors had been detected to prevent their being deliverable to a higher-layer protocol. One possible reason for discarding such a packet could be to free up buffer space.
Short for Internetworking Operating System. The Cisco IOS software is the software that runs on the Cisco products, This platform is integral to the interoperations of network devices in a Cisco internetwork. Cisco IOS includes security, access control,authentication, firewall, encryption, and management services. The main purpose of IOS is to boot the Cisco hardware and begin the optimal transport of data acrossthe internetwork.
A dot address of four groups (orquads) of decimal numbers separated by periods
Short for kilobit per second. One kilobit per second (Kbps) equals 1000 bits persecond (bps). Network performance is best measured in bps, but sometimes numbers are given in bytes per second (Bps). Then, one KBps equals one kilobyte per second,one MBps equals one megabyte per second, and GBps equals one gigabyte per second.
The time delay of data traffic through a network or a switch.
Short for Media Access Control address. MAC Address is a standardized data link layer address that uniquely identifies each device and is required for every port or device that connects to a LAN. Other devices in the network use these addresses to locate specific ports in the network and to create and update routing tables and data structures.MAC addresses are 6 bytes long and are also known as a hardware address, MAC layer address, and physical address.
The MIB file can contain one or more MIB modules. Following are the macros defined in the SMIv1 and SMIv2.OBJECT IDENTIFIEROBJECT-TYPE. The following macro definition is defined only in SMIv1.TRAP-TYPE. The following macro definitions are defined only in SMIv2. MODULE-IDENTITYNOTIFICATION-TYPEOBJECT-IDENTITYOBJECT-GROUPAGENT-CAPABILITIESNOTIFICATION-GROUPMODULE-COMPLIANCETEXTUAL-CONVENTION
Short for Management Information Base. A MIB is a standard set of definitions for exchanging information about hardware and software components. Each MIB contains a group of objects, which specify a structure and format for defining manageable elements.
In administering Internet sites, a netmask is a string of 0's and 1's that mask or screen out the network part of an IP address(IP) so that only the host computer part of the address remains. The binary 1's at the beginning of the mask turn the network ID part of the IP address into 0's. The binary 0's that follow allow the host ID to remain. A frequently-used netmask is 255.255.255.0. (255 is the decimal equivalent of a binary string of eight ones.) Used for a Class C subnet (one with up to 255 host computers), the \".0\" in the \"255.255.255.0\" netmask allows the specific host computer address to be visible.
IP address of the network
Short for nonvolatile RAM. NVRAM is a special memory that does not lose its information when a router is powered off. It stores the system's startup configuration file and the virtual configuration register.
Devices that do not support SNMP.
Short for Non Volatile RAM. NVRAM is a special memory that does not lose its information when a router is powered off. It stores the system's startup configuration file and the virtual configuration register.
Number of octets transmitted over the interface.
Short for Object Identifier. Object identifiers are, basically, strings of numbers. They are allocated in a hierarchical manner, so that, for instance, the authority for \"1.2.3\" is the only one that can say what \"1.2.3.4\" means. They are used in a variety of protocols.
The number of outbound packets which were chosen to be discarded even though no errors had been detected to prevent their being transmitted. One possible reason for discarding sucha packet could be to free up buffer space.
A flow is a set of packets passing an observation point in the network during a certain time interval. All packets belonging to a particular flow have a set of common properties derived from the data contained in the packet and from the packet treatment at the observation point.
Quality of Service standards seek to maximize the use of available network bandwidthby prioritizing time-sensitive traffic.
Short for random-access memory. RAM is a volatile memory that can be read and written by a computer.
The number of inbound packets that contained errors preventing them from being deliverable to a higher-layer protocol.
Reverse DNS lookup uses an Internet IP address to find a domain name.
Short for read-only memory. ROM is the non volatile memory that can be read , but not written , by the computer. The image in ROM is the image the router first useswhen it is powered up. This image is usually an older and smaller version of IOSwithout the features of a full IOS version.
The Round Trip time refers to the timestamp placed by Ping in each packet, which is echoed back to calculate how long each packet exchange took.
An Intermediate System (IS) which operates at the network layer of theOSI reference model. Routers may be used to connect two or more IP networks, or an IP network to an internet connection. A router consists of a computer with at least two network interface cards supportingthe IP protocol. The router receives packets from each interface via a network interface and forwards the received packets to an appropriate output network interface.
Refers to the number of packets that are discarded because they are smaller than the medium's minimum packet size.
Short for Simple Mail Transfer Protocol. A protocol used to transfer electronic mails between computers
A management entity consisting of hardware and embedded software which responds to SNMP requests over Ethernet from an SNMP manager
A subnet (short for \"subnetwork\") is an identifiably separate part of an organization'snetwork. Typically, a subnet may represent all the machines at one geographic location,in one building, or on the same local area network (LAN). This32-bit IP address has two parts: one part identifies the network (with the networknumber) and the other part identifies the specific machine or host within the network(with the host number). An organization can use some of the bits in the machine orhost part of the address to identify a specific subnet. Effectively, the IP addressthen contains three parts: the network number, the subnet number, and the machine number.
A subnet mask is used to determine what subnet an IP address belongs to.
Short for \"Transmission Control Protocol / Internet Protocol\" - TCP/IPis a suite of communications protocols that forms the basis for and defines the Internet.
Value to be set in milliseconds to wait for each packet reply before the connection is disconnected as no data is being sent.
The number of outbound packets that could not be transmitted because of errors.
Short for Time to Live. TTL is a field in the Internet Protocol (IP) that specifies how many more hops a packet can travel before being discarded or returned.
A communications protocol that, like TCP, runs on top of IP networks. Unlike TCP/IP,UDP/IP provides very few error recovery services, offering instead a direct way to send and receive datagrams (a datagram is the term used to describe data that ispacketised for network transport) typically over an IP network. It is used primarilyfor broadcasting messages over a network. UDP uses the Internet Protocol to get datafrom one computer or device to another but does not divide a message into sequenced packets nor reassemble it at the other end