Interior gateways are gateways that belong to the same autonomous system. They communicate with each other using the Routing Information Protocol (RIP), Routing Information Protocol Next Generation (RIPng), Intermediate System to Intermediate System protocol, Open Shortest Path First (OSPF) protocol, or the HELLO Protocol (HELLO). Exterior gateways belong to different autonomous systems. They use the Exterior Gateway Protocol (EGP), the Border Gateway Protocol (BGP), or BGP4+. For example, consider two autonomous systems. The first is all the networks administered by the Widget Company. The second is all the networks administered by the Gadget Company. The Widget Company has one machine, called apple, which is Widget's gateway to the Internet. The Gadget Company has one machine, called orange, which is Gadget's gateway to the Internet. Both companies have several different networks internal to the companies. The gateways connecting the internal networks are interior gateways. But apple and orange are exterior gateways. Each exterior gateway does not communicate with every other exterior gateway. Instead, the exterior gateway acquires a set of neighbors (other exterior gateways) with which it communicates. These neighbors are not defined by geographic proximity, but rather by their established communications with each other. The neighboring gateways, in turn, have other exterior gateway neighbors. In this way, the exterior gateway routing tables are updated and routing information is propagated among the exterior gateways. The routing information is sent in a pair, (N,D), where N is a network and D is a distance reflecting the cost of reaching the specified network. Each gateway advertises the networks it can reach and the costs of reaching them. The receiving gateway calculates the shortest paths to other networks and passes this information along to its neighbors. Thus, each exterior gateway is continually receiving routing information, updating its routing table and then passing that information to its exterior neighbors.
In this article you will learn about definitions of IGP and EGP, also you will get to know about difference between Interior Gateway Protocols and Exterior Gateway Protocol (IGRP vs. EGP). Interior Gateway Protocol (IGP): When the data packets are to be transferred within the same autonomous systems, Interior Gateway Protocols are used (IGP). For the communication to happen between the networks using Interior Gateway Protocol, both the networks must belong to same autonomous system. The router identifies the autonomous system of a network using autonomous system number. If the autonomous system number of two networks is different, we cannot use Interior Gateway Protocol to establish a communication link between those two networks. Generally, there are three categories of Interior Gateway protocols
Distance Vector Protocols: Bellman Ford algorithm is used in distance vector protocols and the routers that uses distance vector protocol does not have information about entire network. The routers advertise the distance value calculated. The distance value information is tabulated as routing table. Some of the examples of protocols that use distance vector protocol are RIP, RIP version2, RIPng, and IGRP etc Link State Protocols: The routers using link state protocol has the information about the entire topology. Based on the information about the topology, routers are capable of selecting best next hop independently. The best next hops are tabulated as routing table. OSPF, IS-IS (Intermediate System to Intermediate System) are some of the example of protocols that uses link state routing protocol. Hybrid Protocol: The hybrid protocols are the combination of distance vector and link state routing protocols. They have the features of both the categories. EIGRP is the best example of Hybrid Protocol. Exterior Gateway Protocol (EGP): Exterior Gateway Protocol is used to transfer the data packets between two different autonomous systems. The router identifies the device autonomous system based on autonomous system number assigned to that network. Exterior Gateway protocol (EGP) and Border Gateway Protocols (BGP) are the examples of Exterior Gateway Protocols. Routers that uses Exterior Gateway Protocol (EGP) maintains the information about all the IP addresses assigned to the devices, best path to a particular network and cost metrics etc. Differences between EGP and IGP Though the Exterior Gateway Protocol and Interior Gateway protocols are used to transmit the data packets between different networks using routable protocols like Internet Protocol; they are different from each other. Interior Gateway Protocol is used to forward the packets among different networks that use the same autonomous system number. Whereas the exterior Gateway Protocol have the capability of forwarding data packets to different networks with different autonomous system numbers. Note: Routing Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS) are IGP Protocols. However BGP (Border Gateway Protocol) is EGP Protocol. Read moreCCNA TutorialCCNA Practice Test
Routing is the process of moving data from one network to another. Routing is unnecessary unless you have multiple networks on different address ranges. If you have different combinations of IP addresses and subnet masks, you have separate networks. If you don't, you need to perform bridging or switching. You don't need to run a routing protocol unless you have multiple networks served by more than one router (and even then, manual static routes are easier for small networks). Once you get beyond three routers, it's time to start thinking about dynamic routing protocols. If you are connecting your networks to the Internet, you will also need to think about running more than one kind of routing protocol. INTERIOR GATEWAY PROTOCOLS Interior Gateway Protocols (IGPs) handle routing within an Autonomous System (one routing domain). In plain English, IGP's figure out how to get from place to place between the routers you own. These dynamic routing protocols keep track of paths used to move data from one end system to another inside a network or set of networks that you administrate (all of the networks you manage combined are usually just one Autonomous System). IGP's are how you get all the networks communicating with each other. IGP's fall into two categories: Distance Vector Protocols Link State Protocols EXTERIOR GATEWAY PROTOCOLS To get from place to place outside your network(s), i.e. on the Internet, you must use an Exterior Gateway Protocol. Exterior Gateway Protocols handle routing outside an Autonomous System and get you from your network, through your Internet provider's network and onto any other network. BGP is used by companies with more than one Internet provider to allow them to have redundancy and load balancing of their data transported to and from the Internet. Examples of an EGP: Bookmark this page and SHARE: |
What is the difference between interior and exterior routing protocols?
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