[SOLVED] Basic IP Address Help

Apr 2, 2020
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Hi,
I cannot get my head around class C addresses and subnetting.
First of all, when someone changes the subnet mask to 255.255.0.0 on a 192.168.1.1, how can that work since it is class C? I was under the impression it had to be 255.255.255.x?
Also, if you have a small LAN, and get advised to have the router's IP as 192.168.10.1 instead of 192.168.1.1, why would that be so? what benefits do you get from it?
Thanks in advance.
 

kanewolf

Titan
Moderator
Hi,
I cannot get my head around class C addresses and subnetting.
First of all, when someone changes the subnet mask to 255.255.0.0 on a 192.168.1.1, how can that work since it is class C? I was under the impression it had to be 255.255.255.x?
Also, if you have a small LAN, and get advised to have the router's IP as 192.168.10.1 instead of 192.168.1.1, why would that be so? what benefits do you get from it?
Thanks in advance.
Second part first. Not using 192.168.1.1 makes it more unique. Many devices have 192.168.1.x as their default IP address. It is more difficult to get those devices accidentally mixed into your network. I would also recommend against 192.168.100.x because most cable modems use that IP address for access.

Your PC is in a class C network just because of the 192.x.y.z -- https://en.wikipedia.org/wiki/Classful_network#Classful_addressing_definition
192.168.x.y is special because it is in the private address space -- https://en.wikipedia.org/wiki/Private_network
 

kanewolf

Titan
Moderator
Hi,
I cannot get my head around class C addresses and subnetting.
First of all, when someone changes the subnet mask to 255.255.0.0 on a 192.168.1.1, how can that work since it is class C? I was under the impression it had to be 255.255.255.x?
Also, if you have a small LAN, and get advised to have the router's IP as 192.168.10.1 instead of 192.168.1.1, why would that be so? what benefits do you get from it?
Thanks in advance.
Second part first. Not using 192.168.1.1 makes it more unique. Many devices have 192.168.1.x as their default IP address. It is more difficult to get those devices accidentally mixed into your network. I would also recommend against 192.168.100.x because most cable modems use that IP address for access.

Your PC is in a class C network just because of the 192.x.y.z -- https://en.wikipedia.org/wiki/Classful_network#Classful_addressing_definition
192.168.x.y is special because it is in the private address space -- https://en.wikipedia.org/wiki/Private_network
 
The whole concept of CLASS is very outdated. It was done to reduce the amount of memory it took to store routing tables. Memory is cheap and processors are huge compared to years ago when they where still using classful routing. Many routers have dropped support for using "classful" summaries.

The terminology is still used but it is getting much more common to just say /24 or /16 rather than class c and class b.
 

anjris

Prominent
Aug 5, 2019
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First of all, when someone changes the subnet mask to 255.255.0.0 on a 192.168.1.1, how can that work since it is class C? I was under the impression it had to be 255.255.255.x?
Yes, 192.168.1.1 is a class C address and its default subnet mask is 255.255.255.0.
But if someone changes its subnet mask to 255.255.0.0 on a 192.168.1.1. It means it will do the super netting as below.

192.168.1.1/16 it means its a summarized route and cover all the subnets in 3rd octet.
192.168.0.0 - 192.168.255.255. it covers very large subnets in a single route.

Also, if you have a small LAN, and get advised to have the router's IP as 192.168.10.1 instead of 192.168.1.1, why would that be so? what benefits do you get from it?
Because generally all the router's have default IP address 192.168.1.1 and it is known to all.
So it is always advisable to change the default login ip address to something unique address for security purpose.

Let me know if my answer still continue to scratch your head.
 

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