What is a Router?
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What is a Router?
Router is a network device which is used to connect two or more different networks.
Router operates at Layer 3(Network Layer) which means that it deals with IP layer.
Routers are expected to perform Layer3(Network Layer) functions, like:
1.Routing
2.Fragmentation
To learn more about this topic you can refer to – OSI- Network Layer lesson.
Router is a smart device.
As router connects different networks, it has knowledge about the networks which are directly connected to it.
This network information is stored inside a special table called Routing Table.
Whenever a packet comes to an interface of a router, it performs lookup for the destination IP address in the routing table and checks if it knows about the destination network where the packet wants to go to.
It is important to remember that if a router doesn’t know about the destination network, in that case the packets going to such destination are dropped.
This is unlike switch, where a switch floods the frame via its switchports if it doesn’t know how to reach a destination MAC Address.
Every network connected to a router makes up a different broadcast domain.
So if a Router has 10 networks connected to it, then there will be 10 different broadcast domains, one for each network.
This means that if there is a message being broadcasted in “A Network”, then this message will not be forwarded by the router to “B Network” or any other network connected to it.
Router limits the flooding of broadcast messages.
Fragmentation
Fragmentation is the process of dividing a single packet into smaller sub-packets.
This concept is related to the maximum packet size that is allowed to traverse a particular network.
The term for this is called as MTU – Maximum Transmission Unit
MTU defines the maximum size of packet that can be transmitted over a network.
If the packet that has been received on a router’s interface is of big size, and it has to be forwarded out another interface where the maximum packet size allowed is smaller, then fragmentation needs to be performed by the router.
Nice read.
Thanks Neeraj, glad you liked it 🙂