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EIGRP
Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary protocol, available only on Cisco routers. In 2013 Cisco decided to allow other vendors freely implement limited version of EIGRP with some of its associated features such as High Availability (HA), while withholding other EIGRP features such as EIGRP stub, needed for DMVPN and large-scale campus deployment, exclusively for themselves. Information needed for implementation was published with informational status as in 2016, which did not make it into an Internet Standards Track specification and allowed Cisco to retain control of the EIGRP protocol. EIGRP is used on a router to share routes with other routers within the same autonomous system. Unlike other well known routing protocols, such as RIP, EIGRP only sends incremental updates, r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffusing Update Algorithm
The diffusing update algorithm (DUAL) is the algorithm used by Cisco's EIGRP routing protocol to ensure that a given route is recalculated globally whenever it might cause a routing loop. It was developed by J.J. Garcia-Luna-Aceves at SRI International. The full name of the algorithm is DUAL finite-state machine (DUAL FSM). EIGRP is responsible for the routing within an autonomous system, and DUAL responds to changes in the routing topology and dynamically adjusts the routing tables of the router automatically. EIGRP uses a feasibility condition to ensure that only loop-free routes are ever selected. The feasibility condition is conservative: when the condition is true, no loops can occur, but the condition might under some circumstances reject all routes to a destination although some are loop-free. When no feasible route to a destination is available, the DUAL algorithm invokes a diffusing computation to ensure that all traces of the problematic route are eliminated from the n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protocol-dependent Module
Protocol-dependent modules (PDMs) are used by the routing protocol EIGRP to make decisions about adding routes learned from other sources; for example other routers or routing protocols to the routing table. In fact EIGRP has the capability for routing several different protocols including IPv4 and IPv6 using protocol-dependent modules (PDMs). The PDM is also capable of carrying information from the routing table to the topology table. EIGRP offers support for various routed protocols (e.g. Internet Protocol Version 6 (IPv6), IP, IPX, AppleTalk), and has added support for Service Routing ( SAF) PDMs. The only other routing protocol that comes with support for multiple network layer protocols is Intermediate System-to-Intermediate System (IS-IS). "In theory, EIGRP can add PDMs to easily adapt to new or revised routed protocols such as IPv6. Each PDM is responsible for all functions related to its specific routed protocol. The IP-EIGRP module is responsible for the following funct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Routing Protocol
A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network. Routers perform the traffic directing functions on the Internet; data packets are forwarded through the networks of the internet from router to router until they reach their destination computer. Routing algorithms determine the specific choice of route. Each router has a prior knowledge only of networks attached to it directly. A routing protocol shares this information first among immediate neighbors, and then throughout the network. This way, routers gain knowledge of the topology of the network. The ability of routing protocols to dynamically adjust to changing conditions such as disabled connections and components and route data around obstructions is what gives the Internet its fault tolerance and high availability. The specific characteristics of routing protocols include the manner in which they avoid rou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Route Summarization
A supernetwork, or supernet, is an Internet Protocol (IP) network that is formed by aggregation of multiple networks (or subnets) into a larger network. The new routing prefix for the aggregate network represents the constituent networks in a single routing table entry. The process of forming a supernet is called supernetting, prefix aggregation, route aggregation, or route summarization. Supernetting within the Internet serves as a strategy to avoid fragmentation of the IP address space by using a hierarchical allocation system that delegates control of segments of address space to regional Internet registries. This method facilitates regional route aggregation. The benefits of supernetting are efficiencies gained in routers in terms of memory storage of route information and processing overhead when matching routes. Supernetting, however, can introduce interoperability issues and other risks. Overview In IP networking terminology, a supernet is a block of contiguous subnetw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Routing Information Protocol
The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from source to destination. The largest number of hops allowed for RIP is 15, which limits the size of networks that RIP can support. RIP implements the split horizon, route poisoning, and holddown mechanisms to prevent incorrect routing information from being propagated. In RIPv1 routers broadcast updates with their routing table every 30 seconds. In the early deployments, routing tables were small enough that the traffic was not significant. As networks grew in size, however, it became evident there could be a massive traffic burst every 30 seconds, even if the routers had been initialized at random times. In most networking environments, RIP is not the preferred choice of routing protocol, as its time to converge and scalability are poor compa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distance-vector Routing Protocol
A distance-vector routing protocol in data networks determines the best route for data packets based on distance. Distance-vector routing protocols measure the distance by the number of routers a packet has to pass; one router counts as one hop. Some distance-vector protocols also take into account network latency and other factors that influence traffic on a given route. To determine the best route across a network, routers using a distance-vector protocol exchange information with one another, usually routing tables plus hop counts for destination networks and possibly other traffic information. Distance-vector routing protocols also require that a router inform its neighbours of network topology changes periodically. Distance-vector routing protocols use the Bellman–Ford algorithm to calculate the best route. Another way of calculating the best route across a network is based on link cost, and is implemented through link-state routing protocols. The term ''distance vector'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interior Gateway Routing Protocol
Interior Gateway Routing Protocol (IGRP) is a distance vector interior gateway protocol (IGP) developed by Cisco. It is used by routers to exchange routing data within an autonomous system. IGRP is a proprietary protocol. IGRP was created in part to overcome the limitations of RIP (maximum hop count of only 15, and a single routing metric) when used within large networks. IGRP supports multiple metrics for each route, including bandwidth, delay, load, and reliability; to compare two routes these metrics are combined into a single metric, using a formula which can be adjusted through the use of pre-set constants. By default, the IGRP composite metric is a sum of the segment delays and the lowest segment bandwidth. The maximum configurable hop count of IGRP-routed packets is 255 (default 100), and routing updates are broadcast every 90 seconds (by default). IGRP uses protocol number 9 for communication.{{cite web , url=https://www.iana.org/assignments/protocol-numbers/protocol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Administrative Distance
Administrative distance (AD) or route preference is a number of arbitrary unit assigned to dynamic routes, static routes and directly-connected routes. The value is used in routers to rank routes from most preferred (low AD value) to least preferred (high AD value).Cisco Systems (2013),What is Administrative Distance? retrieved 14 September 2013 When multiple paths to the same destination are available in its routing table, the router uses the route with the lowest administrative distance. Router vendors typically design their routers to assign a default administrative distance to each kind of route. For example, on Cisco routers, routes issued by the Open Shortest Path First routing protocol have a lower default administrative distance than routes issued by the Routing Information Protocol. This is because, by default on Cisco routers, OSPF has a default administrative distance of 110 and RIP has a default administrative distance of 120. Administrative distance values can, howe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Routing
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone network (PSTN), and computer networks, such as the Internet. In packet switching networks, routing is the higher-level decision making that directs network packets from their source toward their destination through intermediate network nodes by specific packet forwarding mechanisms. Packet forwarding is the transit of network packets from one network interface to another. Intermediate nodes are typically network hardware devices such as routers, gateways, firewalls, or switches. General-purpose computers also forward packets and perform routing, although they have no specially optimized hardware for the task. The routing process usually directs forwarding on the basis of routing tables. Routing tables maintain a record of the routes to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Routing
Dynamic routing, also called adaptive routing, is a process where a router can forward data via a different route for a given destination based on the current conditions of the communication circuits within a system. The term is most commonly associated with data networking to describe the capability of a network to 'route around' damage, such as loss of a node or a connection between nodes, so long as other path choices are available. Dynamic routing allows as many routes as possible to remain valid in response to the change. Systems that do not implement dynamic routing are described as using static routing, where routes through a network are described by fixed paths. A change, such as the loss of a node, or loss of a connection between nodes, is not compensated for. This means that anything that wishes to take an affected path will either have to wait for the failure to be repaired before restarting its journey, or will have to fail to reach its destination and give up the journ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Link-state Routing Protocol
Link-state routing protocols are one of the two main classes of routing protocols used in packet switching networks for computer communications, the others being distance-vector routing protocols. Examples of link-state routing protocols include Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS). The link-state protocol is performed by every ''switching node'' in the network (i.e., nodes that are prepared to forward packets; in the Internet, these are called routers). The basic concept of link-state routing is that every node constructs a ''map'' of the connectivity to the network, in the form of a graph, showing which nodes are connected to which other nodes. Each node then independently calculates the next best logical ''path'' from it to every possible destination in the network. Each collection of best paths will then form each node's routing table. This contrasts with distance-vector routing protocols, which work by having each node shar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Incremental Computing
Incremental computing, also known as incremental computation, is a software feature which, whenever a piece of data changes, attempts to save time by only recomputing those outputs which depend on the changed data. When incremental computing is successful, it can be significantly faster than computing new outputs naively. For example, a spreadsheet software package might use incremental computation in its recalculation feature, to update only those cells containing formulas which depend (directly or indirectly) on the changed cells. When incremental computing is implemented by a tool that can implement it for a variety of different pieces of code automatically, that tool is an example of a program analysis tool for optimization. Static versus dynamic Incremental computing techniques can be broadly separated into two types of approaches: ''Static approaches'' attempt to derive an incremental program from a conventional program P using, e.g., either manual design and refactoring ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
