Since each OSPF router has a copy of the topology database and routing table for its particular area, any route changes are detected faster than with distance vector protocols and alternate routes are determined. Designated routers establish adjacencies with all routers on that network segment. This is to reduce broadcasts from all routers sending regular hello packets to its neighbors. The DR sends multicast packets to all routers that it has established adjacencies with.
Each router is assigned a router ID, which is the highest assigned IP address on a working interface. An intermediate system is a router and IS-IS is the routing protocol that routes packets between intermediate systems. Neighbor routers on point to point and point to multipoint links establish adjacencies by sending hello packets and exchanging link state databases. IS-IS routers on broadcast and NBMA networks select a designated router that establishes adjacencies with all neighbor routers on that network.
The designated router and each neighbor router will establish an adjacency with all neighbor routers by multicasting link state advertisements to the network itself. IS-IS uses a hierarchical area structure with level 1 and level 2 router types. Level 1 routers are similar to OSPF intra-area routers, which have no direct connections outside of its area. Level 2 routers comprise the backbone area which connects different areas similar to OSPF area 0.
The difference with IS-IS is that the links between routers comprise the area borders and not the router. Each IS-IS router must have an assigned address that is unique for that routing domain.
An address format is used which is comprised of an area ID and a system ID. There is support for variable length subnet masks, which is standard with all link state protocols.
Note that IS-IS assigns the routing process to an interface instead of a network. Border Gateway Protocol is an exterior gateway protocol , which is different from the interior gateway protocols discussed so far. Exterior gateway protocols such as BGP route between autonomous systems, which are assigned a particular AS number.
AS numbers can be assigned to an office with one or several BGP routers. The difference is their autonomous systems refer to a logical grouping of routers within the same administrative system. They are all managed by the company for defining route summarization, redistribution and filtering.
BGP is utilized a lot by Internet Service Providers ISP and large enterprise companies that have dual homed internet connections with single or dual routers homed to the same or different Internet Service Providers. BGP will route packets across an ISP network, which is a separate routing domain that is managed by them.
There are 10 defined attributes that have a particular order or sequence, which BGP utilizes as metrics to determine the best path to a destination. Companies with only one circuit connection to an ISP will implement a default route at their router, which forwards any packets that are destined for an external network. Once that is finished, incremental updates are sent with topology changes.
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It also runs on the Application layer of the OSI model. Two versions of RIP are. The original version or RIPv1 helps you determine network paths based on the IP destination and the hop count journey.
RIPv1 also interacts with the network by broadcasting its IP table to all routers connected with the network. It is introduced to overcome RIP limitations. The metrics used are load, bandwidth, delay, MTU, and reliability. It is widely used by routers to exchange routing data within an autonomous system. This type of routing protocol is the best for larger network size as it broadcasts after every 90 seconds, and it has a maximum hop count of It helps you to sustain larger networks compared to RIP.
IGRP is also widely used as it is resistant to routing loop because it updates itself automatically when route changes occur within the specific network. It is also given an option to load balance traffic across equal or unequal metric cost paths.
Link State Protocols take a unique approach to search the best routing path. In this protocol, the route is calculated based on the speed of the path to the destination and the cost of resources. EGP is a protocol used to exchange data between gateway hosts that are neighbors with each other within autonomous systems. This routing protocol offers a forum for routers to share information across different domains. EGP protocol includes known routers, network addresses, route costs, or neighboring devices.
Also if some link fails and there is one more path, traffic will be redirected to other path automatically. Cool, right? There are three categories in IGP,. Distance Vector Routing Protocols work on distance how far the destination is? DVRP measure distance in terms of hop counts which means how many networks it has to cross if it want to reach the destination. Means in which direction, hop count is less? They also have complete information of network like a map. There is no limit of size.
Network can be big or small, it will work efficiently. Other one is IS-IS. These are also much better than DVRP in term of convergence. EIGRP routing protocols comes under this category. It uses properties of distance vector protocol to reduce the processing power requirement, but exchanges routing table information only when their tables change to reduce transmission overhead.
EIGRP also insure that routing loop never occurs in a network. Default routing can be used with Static Routing. But if there is a default route, that unknown packet will be forwarded to the address associated with default route. Great to read this informative article. And i have created a topology where I have 2 routers connected with 2 cables with static routing and same ad value? Yes, BGP is indeed one the best protocols available but it takes a lot of CPU usage plus it it a bit hard to configure in a network.
In static routing, packet will always be forwarded as per your configuration. Other path will be used as a backup path. When one link fails, then only packet will be forwarded to other. Surendra Singh Sr. Ltd We believe in practical training. Your email address will not be published.
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