Interior gateway Routing protocols
Interior gateway protocols or IGPS are a category of protocols used within autonomous networks. Autonomous networks are networks that you control or that are under the control of a single organization. The most popular IGP protocols are OSPF, open shortest path first and rip version two. That’s routing information protocol version two.
Now there is a special mention here. And that’s is which is intermediate system to intermediate system is popular with extremely large autonomous networks. Like an ISP. These are Internet Service Providers’ networks.
Exterior gateway protocols
Exterior gateway protocols, on the other hand, are a category of protocols used between nonautonomous networks. So EG peas are used between networks that are controlled by different organizations or entities. The most popular EGP protocol is the Border Gateway Protocol.
No, it’s not uncommon for organizations to have more than one network where they are routing traffic. These are called autonomy networks. Some IGP routing protocols use an administrator-defined autonomous system number or AAS number as one means of identifying which networks can directly communicate with each other.
The autonomous system number is not a metric, but a means of identifying a network that might possibly accept another network’s traffic. Something to remember is that the AAS is only significant within autonomous networks, and has no relevance outside of them. Now let’s move on to more routing concepts. Routing protocols can be classified by how they perform thorough routing, interior gateway, and EGP.
Routing protocols can be broken out into three other categories of protocols, which are designated by their main method of determining routes between networks.
The first class of routing protocols is distance vector routing protocols. With distance vector routing protocols, the routes are determined by how many routers exist between the source and the destination, the efficiency of the links in the selected route is not taken into consideration with distance vector protocols.
Periodically, the whole routing table is broadcast out onto the network, then there are link state routing protocols, and metrics are used to determine the best possible route between destinations doesn’t really matter how many hops there are, once the route has been established. These protocols then only monitor the state of directly connected links and only make changes to their routing tables.
When changes to the links occur. With link state routing protocols, only changes in the link status are broadcasted finally there are hybrid routing protocols. These use aspects of both the distance vector and link state routing protocols. Let’s talk about the next hop. The next hop is the next router in the path between two points.
The next hop is often designated by an interface address of the device that is receiving the data or by that router’s name or by that router’s location. The routing table is the database table that is used by a router to determine the best possible route between two points. Different routing protocols use different algorithms to place routes in the routing table.
The next concept is convergence. Convergence can be thought of as a steady state. Convergence is measured in the amount of time that it takes all of the routers in an autonomous system to learn all of the possible routes within that system.
Faster convergence times are desirable as that steady state allows routing to occur more quickly. Now let’s move on to the routing protocols themselves. First, up is routing information protocol. Version two rip version two. Rip is an IGP distance vector protocol. For a route to be placed in the routing table.
It can be no more than 15 hops away. A hop count of 16 is considered unreachable. It uses various methods including the hop count to reduce the chances of a routing loop occurring. Rip version two uses multicast address 220 4.0 dot 0.9. to advertise its routing table. The open shortest path first OSPF is the most popular IGP that’s currently being used.
It is a link state routing protocol. It uses the Dijkstra algorithm to determine the shortest path to a network. after its initial start-up, it only advertises changes to its routing table making convergence much faster. It uses different types of link state advertisements or lSATS to announce different changes or different operations.
OSPF uses two multicast addresses 220 4.0 dot 0.5 or 220 4.0 dot 0.6 depending upon the type of LSA, that it’s transmitting, next up intermediate system to intermediate system or is a link state routing protocol like OSPF and similar to OSPF it to uses the Dijkstra algorithm, but it uses different metrics to determine the best path is highly scalable.
It offers fast convergence often found within networks under the control of an internet service provider. Then there’s Border Gateway Protocol BGP, it’s an exterior gateway protocol. That’s also a hybrid routing protocol. It is considered the routing protocol of the internet.
And as a hybrid protocol, it is often considered a path vector protocol, which makes it hybrid. One of the metrics used is the number of autonomous systems that must be crossed, not individual routers, BGP is highly scalable, but has a very slow convergence time when changes do occur.
As a special mention, I’m going to talk about an enhanced interior gateway routing protocol, IE EIGRP. It is an advanced distance vector or hybrid IGP routing protocol developed by Cisco in 2013. Cisco made AIG RP, an open-source routing protocol and an effort to increase its use in autonomous networks.
It uses aspects of both the distance vector protocol and the link state protocol to build its routing table. EI GRP has a very fast convergence time. But it’s not as popular as OSPF because OSPF has been open source longer than EEI GRP EI GRP uses a neighbour table, which is directly connected to routers, and a topology table to build its routing table.
The protocol only announces changes to the routing table on multicast address 224 dot 0.0 dot 10 in order to reduce bandwidth consumption.
In this article, we talked about the differences between interior and exterior gateway protocols I mentioned some more routing concepts, and we concluded with the routing protocols themselves.
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