How exactly do subnet masks work in terms of how packets are delivered?

272 viewsOtherTechnology

I’m studying for a certification at the moment so I know a medium amount about the structure of subletting. The one thing my courses don’t explain very well is the actual function/process of how this works.

Specifically one thing I learned really upended my understanding. The example was if you have a host with the address 10.1.16.42/24 and a host with the address 10.1.16.200/16 would they need a router to communicate?

From my understanding they would, the first host is on the network 10.1.16 and the host section is 42. The second one is on 10.1 and the host section is 16.200. Since their network sections are different why do they not need a router to communicate if their network id’s aren’t the same?

In: Technology

6 Answers

Anonymous 0 Comments

It’s a misconfiguration, but their LANs happen to overlap such that it works out and they happen to each think they’re on the same LAN segment.

The subnet mask describes what IP ranges the device will try to connect directly to and what ranges it will ask the defined gateway for help with. In this case let’s say host A is 10.1.16.42/24 and host B is 10.1.16.200/16.

If A wants to talk to B it looks at B’s address and sees that B’s address is within the LAN defined by the CIDR prefix – B has the same first 24 bits of A’s address or 10.1.16. So it can talk directly to B.

If B wants to talk to A it sees that A’s first 16 bits are the same 10.1 it has in its LAN definition. So it can talk to A directly.

This would break down if A were 10.1.1.42/24 because then A would recognize itself as being on a different LAN segment than B, but B would still think it was on the same LAN segment as A.

You are viewing 1 out of 6 answers, click here to view all answers.