Dynamic routing protocols are another important type of routing protocol. It helps routers automatically add information from connected routers to their routing tables. These protocol types also send topology updates when the topology structure of the network changes. Routing protocols help routers learn routes by each router by announcing routes they know. Each router starts by knowing only the directly connected routes. Then, each router sends messages defined by the routing protocol that list routes. When one router hears a routing update message from another router, the router listening for the update discovers the subnets and adds routes to its routing table. If all routers participate, all routers can get to know all the subnets on a network. These protocols measure distance based on the number of hops the data must pass through to reach its destination. The number of hops is basically the number of routers needed to reach the destination.
The Interior Gateway Routing Protocol (IGRP) was developed by Cisco to solve RIP problems in large networks. IGRP is a distance vector protocol, but it uses several routing metrics (not just the number of hops) to determine the distance to the destination. IGRP offers features to improve stability such as updates, split horizons, and poisoned reverse updates. IGRP should only be used if your current environment consists entirely of IGRP and you do not want to introduce another routing protocol. Deductions. Used to prevent a periodic update message from restoring a route that may have been faulty in the past. When a network connection fails, neighboring routers detect the lack of regular updates and find that the connection is not working. The update messages then begin to penetrate the network because this router is not working.
If this convergence takes too long, it is possible that another router on the network will announce that this router is still working normally. This device may publish incorrect routing information. A hold requires routers on the network to hold back any changes that may affect the routes for a period of time. The waiting period is calculated to be only slightly longer than the time it takes to update the entire network with a routing change. Poisoned reverse updates. Used to minimize loops between more than two routers. If the metric increases significantly, it may indicate a routing loop. A poisoned reverse update is then sent to the router to put it on hold.
Routing protocols merge and cannot merge all these ASs into a homogeneous whole. Routing protocols allow routers or networks to share neighborhood information with their neighbors. They provide global connectivity between routers inside and outside an AS, and ASs, in turn, provide the global connectivity that characterizes the Internet. Routing policies change the behavior of routing protocols so that AS connectivity becomes what ISPs want (typically, ISPs add a term such as “AS connectivity is made more effective and efficient,” but often the routing strategy does not, as we`ll see). Once you know how to categorize routing protocols, you can learn more about the seven different types. While each router can have similar login information to the map database, it can also use the shortest algorithm to complete navigation. A protocol for exchanging connection information between each router is called a routing protocol. This article just wants to get you to speed up the so-called routing protocol.
So far, you should understand what routing is, but what about the protocol? The protocol specifies how this connection information is expressed, how much it costs to pass through this connection, and which node routers are located at each end of this connection. With this information, routers can dynamically draw a map (topology diagram) of the entire network. For each destination, a routing entry is dynamically generated according to the shortest path algorithm and inserted into a table that we call a routing table. IGRP is a distance vectorization protocol in which routers (often called gateways) exchange routing information only with neighboring routers. When the neighboring router receives the update, it compares the information to its own route table. All new paths or destinations are added. The paths in the neighboring router update are also compared to the existing paths to determine if the new route is more efficient than the path that currently exists in the route table. If the new path is better, it replaces the existing path.
This is the general procedure used in all distance vector protocols. Integrated Staging System – The Staging System Routing Protocol is a link state protocol similar to OSPF used by large enterprises and ISP customers. An intermediate system is a router and IS-IS is the routing protocol that forwards packets between intermediate systems. IS-IS uses a link state database and runs the Dijkstra SPF algorithm to select the shortest routes. Neighboring routers on point-to-point and point-to-multipoint connections establish adjacent connections by sending hello packets and exchanging link state databases. IS-IS routers on broadcast and NBMA networks select a specific router adjacent to neighboring routers on that network. The designated router and each neighboring router establish a neighborhood for all neighboring routers by delivering link status ads to the network itself. This is different from OSPF, which only establishes adjacent connections between the DR and each adjacent router. IS-IS uses a hierarchical scope structure with Tier 1 and Tier 2 router types. Tier 1 routers are similar to OSPF intra-zone routers that do not have direct connections outside their territory. Level 2 routers include the backbone, which connects different areas similar to OSPF 0. With IS-IS, a router can be an L1/L2 router, which is like an OSPF zone boundary router (ABR) that has connections to its zone and backbone.
The difference with IS-IS is that the connections between routers include range limits and not the router. Each IS-IS router must be assigned a unique address to this routing domain. An address format is used, which consists of a range ID and a system ID. The range ID is the assigned range number and the system ID is a MAC address of one of the router`s interfaces. Subnet masks of varying length are supported, which is standard for all link state protocols. Note that IS-IS assigns the routing process to an interface instead of a network. Link state routing protocols use the cost of the path to the destination as a metric for optimal routing and do not rely on periodic route updates to manage the topology table. Routing information is exchanged only when new adjacent boundaries are set and the neighboring table is created, after which only changes are sent by the link state update (LSU) generated by event. Routing protocols can help computer networks communicate effectively and efficiently. Regardless of the size of the network, these protocols can help transfer data securely to its destination.
Understanding the different categories and types is helpful in understanding which routing practice can best suit your needs. This article discusses five common categorizations of routing protocols and the seven associated protocol types. After talking about the routing table, let`s talk about how IP packets get to the router and how to find the routing table and complete the IP packet navigation task. How to find the next jump with maximum efficiency and accuracy? The dump timer specifies the time that must elapse before a route is emptied from a route table. The default value for the IGRP dump timer is seven times the update period. There are two main types of routing protocols, although many different routing protocols are defined with these two types. Link state and distance vector protocols include primary types. Divided horizons. Used to avoid routing loops between two routers. It never makes sense to return information about the route in the direction from which the packet was sent. In Figure 6.4, router1 announces a route to network A to which it is directly connected. Router2 should never report this route to router1 because router1 is closer to network A.
This prevents routing loops between the two routers. For example, if the interface of network A is down, router2 can still inform router1 that it can reach network A through router1 (which is itself). Router1 could be tricked into believing that this route is correct, and then a routing loop would occur. (Keep in mind that divided horizons only avoid looping between two routers.) IGPs are routing protocols that exchange routing information with other routers within a single autonomous system (AS). An SA is defined as a network or set of networks under the control of a company. AS is therefore separate from the AS ISP. Convergence with EIGRP is faster because it uses an algorithm called a double update algorithm, or DUAL, that runs when a router detects that a particular route is unavailable. The router polls its neighbors for a viable successor. This is defined as a neighbor with the least expensive route to a specific destination that does not cause routing loops.
EIGRP updates its route table with the new route and associated metric. Route changes are only announced to the affected routers when changes occur.