Distance vector routing protocols include: 1. RIP (Routing Information Protocol), which is a routing protocol based on the distance vector algorithm and uses hop count as the measurement standard; 2. IGRP (Interior Gateway Routing Protocol), which is A protocol for exchanging routing information between gateways (hosts and routers) within an autonomous network; 3. EIGRP (Enhanced IGRP).
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
Distance vector routing protocol (English: distance-vector routing protocol) is one of the two major categories of routing protocols. This type of protocol uses the distance vector (distance-vector, abbreviated as DV) algorithm to determine the routing protocol. The path for text exchange. Algorithms including Bellman-Ford algorithm, Ford-Fulkerson algorithm and DUAL FSM are all classified as distance vector algorithms.
Distance vector routing protocols include RIP, IGRP and EIGRP.
RIP
RIP (Routing Information Protocol) is a routing protocol based on the distance vector algorithm, using hop count as the measurement standard, originally in RFC 1058 definition.
Mainly have the following characteristics:
． Use hop count as a metric for path selection.
． If a network has more than 15 hops, RIP cannot provide a route to that network.
． By default, routing updates are sent every 30 seconds via broadcast or multicast.
IGRP
IGRP (Interior Gateway Routing Protocol) is a proprietary protocol developed by Cisco. The main design features of IGRP are as follows:
． Use composite metrics based on bandwidth, latency, load, and reliability.
． By default, routing updates are sent via broadcast every 90 seconds.
． IGRP is the predecessor of EIGRP, which is no longer used.
EIGRP
EIGRP (Enhanced IGRP) is a Cisco-specific distance vector routing protocol. EIGRP mainly has the following features:
． Ability to perform unequal load balancing.
． The shortest path is calculated using the diffusion update algorithm (DUAL).
． No regular updates are required like RIP and IGRP. Routing updates are sent only when the topology changes
Extended information:
The meaning of distance vector
As the name suggests, distance vector means advertising routes using distance and direction vectors. Distance is determined using a metric such as hop count, while direction is the next-hop router or outgoing interface.
Routers that use distance vector routing protocols do not know the entire path to the destination network. The router only knows:
In which direction or interface to forward the data packet
The distance between itself and the destination network
Distance vector routing protocol How it works
Some distance vector routing protocols require routers to periodically broadcast the entire routing table to each neighbor. This approach is inefficient because not only do these routing updates consume bandwidth, but they also consume router CPU resources to process.
Distance vector routing protocols have some common characteristics.
Send periodic updates at certain intervals (RIP’s interval is 30 seconds, IGRP’s interval is 90 seconds). Even if the topology does not change for several days, periodic updates are continuously sent to all neighbors.
Neighbors refer to other routers that use the same link and are configured with the same routing protocol. A router only knows the network address of its own interface and the remote network addresses that can be reached through its neighbors. It knows nothing about other parts of the network topology. Routers using distance vector routing do not understand the network topology.
Broadcast updates are sent to 255.255.255.255. Neighboring routers configured with the same routing protocol will handle such updates. All other devices also process such updates at layers 1, 2, and 3 and then discard them. Some distance vector routing protocols use multicast addresses instead of broadcast addresses.
Regularly sends updates to the entire routing table to all neighbors (but there are some exceptions, which we will discuss later). Neighbors receiving these updates must process the entire update, find useful information in it, and discard the rest. Some distance vector routing protocols, such as EIGRP, do not send routing table updates periodically.
The role of algorithm
The core of the distance vector protocol is the algorithm. Algorithms are used to calculate the best path and send this information to neighbors.
Algorithms are steps used to accomplish a specific task, starting from a given initial state and ending in a defined end state. Different routing protocols use different algorithms to add routes to routing tables, send updates to neighbors, and determine paths.
The algorithm used for routing protocols defines the following process:
The mechanism for sending and receiving routing information.
Mechanism to calculate the best path and add routes to the routing table.
Mechanism to detect and respond to topology changes.
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