IPv4 Addresses

HI

I have a fair understanding of networking (or I thought) until recently when I read something which blew my mind and blew my understanding completely off now, and has had me thinking about it and it's starting to annoy me!

Obviously on a network, Class A address can hold the most hosts
Although, Class C addresses can only hold 253 hosts.
So, when you're joined on a domain and my computer has IP address 192.168.20.1 but the guy next to me has 192.168.21.1, we are on a different network? Correct? So we cannot share resources etc without going through a\the server? Even though we're on the same domain?

I'm all confused, I thought I had complete understanding of IP addressing but obviously not, if someone could take the time to explain it would be greatfully appreciated

Also, DNS, can someone please explain a little about DNS. I have a server setup for personal, hands on experience (she's my drug monkey

) and I have the domain setup completely, but can someone just explain DNS? I understand when you create a server you're required a name for the server (fileserver1.microsoft.com) for example and then you create a random DNS address that can be anything, then you have to configure your clients for that? So, how does secondary DNS come into this (preferred DNS and secondary DNS?)

Thanks in advance for time, effort and replies.

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Comments

benbuiltpc

The 2 examples you gave may or may not be in the same network. It completely depends on the subnet mask. An IP address alone is not enough information. You definately don't need to be on the same network in order to share resources. For example, the server that hosts this website could be on the other side of the world but you can still access it's resources. That's when routers start to come into play.

DNS in a Windows environment is another broad topic, but typically the domain controller(s) is the (one of the) DNS server. The clients or other servers connected to it use it to translate host names to IP addresses.

For a complete understanding of both topics, I would recommend starting with some good A+ and Network+ training materials, then MCSE/MCSA books for implementing DNS in a Microsoft environment.

blargoe

In the real world companies might not be using /8, /16, or /24 for a netmask, but use classless routing instead. I don't remember if they speak to that at all in intro networking classes.

hypnotoad

If your mask is 255.255.255.0 (the default), then 192.168.20.1 and 192.168.21.1 are on different networks. Systems on different networks must go through a router (or more commonly a switch with routing) to talk to each other.

However, your mask might be something completely different, which adjusts the address space so .20 and .21 are on the same network, and then no routing mechanism is neccessary!