Routing is the main function of the router. With routing, you can route the traffic to different paths making your network connected to other networks.
For example, if you have a company with 50 routers, then the traffic would take different paths to go from a source to a destination address. With routing, you can enforce the traffic to go from a definite path rather the other paths.
Routing works on Layer 3, that means you should have IP addresses set before doing the routing.
You have 2 different routing categories:
- Interior Gateway Protocol (IGP)
- Exterior Gateway Protocol (EGP)
To make it more clear for you, let me show you this in an illustration:
Interior Gateway Protocols are routing protocols which work inside the same Autonomous System (AS).
An AS is a set of routers connected to each other and under the responsibility of a network administrator. Think of a network in a hotel, ISP, hospital, company, etc.… When you are responsible for set of routers in your network, then you can run IGP protocols to do the routing.
When you want to do routing between 2 different AS’s, then you need to use the Exterior Routing Protocol (EGP). The only protocol that we have now nowadays working as EGP is the Border Gateway Protocol (BGP).
BGP is the routing protocol of the internet, without BGP we wouldn’t have internet nowadays. What BGP does, it glues the ISP networks to each other so we can, for example, reach to google.com server which is a server somewhere in the United States.
We now understand that we do have IGP and EGP routing protocols and we understand the difference between them.
Let me explain to you now about the static and dynamic routing protocols.
If you have a small network, you can deploy a static routing protocol. That means you have to make the routes manually. You can just create a route for example and say: to reach to that destination network, send all the traffic from this gateway.
The problem with the static routing protocol is that in case the route became down due to any reason like cable failure, port failure, then you need to go to the router and make another route to be like a successor to the main one. That’s why it is advisable to use static route only on a small network but not on a big network.
This type of routing protocols works dynamically. All you need to do is to enable the routing protocol on the routers, and the routers will teach each other about the available routes.
You have 2 type of dynamic routing protocols:
- Distance vector: Such as RIP
- Link state: such as OSPF, IS-IS
Also, BGP is considered a dynamic routing protocol but in the EGP. While RIP, OSPF, and IS-IS are dynamic routing protocols in IGP.
MikroTik supports the following dynamic routing protocol:
- RIP: shown in the routing table as “R”
- OSPF: shown in the routing table as “O”
- BGP: shown in the routing table as “B”