Biren Ajmera asked 2 years ago
I was going through the DNS & Route 53 chapter of the Solutions Architect video training and have a question. So I understand the DNS service basically resolves the resource name (www.example.com) to an ip address (100.100.100.100) by querying a bunch of DNS servers. But after the ip address is available, how does the client computer know where that server with ip 100.100.100.100 is located? I mean how does the request from the client get physically routed to the server after it’s ip address is known?
Faizal Khan Staff answered 2 years ago
This is where the network routers and route tables come in. Every router in the network has a list of IPs of its nearest neighbours. So, essentially what happens is the data (network packets) keep getting passed on from one router to another till it reaches the destination router.
To make this routing possible, routers use route tables and protocols such as OSPF as well as something called AS numbers (ASN) to determine which path to take to reach the IP as soon as possible. Each IP is part of a larger group of IPs that is registered under an ASN. So, ideally speaking, the packet just has to be forwarded till the ASN and from there it is internal network which routes it.
To see this routing in action, you can run a traceroute command to an IP on the command line and you can see all the hops/routers the packet travels through to reach its eventual destination. And if you repeat the same at a different time you might see it take a different path, i.e not the same always. This is the job of OSPF protocol (Open Shortest Path First) to create that route mapping into a route table entry.
If all this sounds a little complicated, you are not alone, this is why there are CCNA, CCNP and CCIE courses, to learn this very routing! 😀
INR ₹
USD $