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Network Number And Network ID?


Invisible§niper
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Hi again everyone,

Just would like to know does the term "Network Number" and "Network ID" refer to the same thing. I mean if I was to have an IP address of:

192.168.1.50

And a subnet of:

255.255.255.0

Wouldn't that mean that the first 3 octets are for my "Network Number" but what's so special about 192.168.1.0 are they the same thing?

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I'm not sure what your question is. You're correct that the Network Number or Network ID of the address 192.168.1.50 with a 255.255.255.0 mask is 192.168.1.0. Any PC on the 192.168.1.0 subnet (meaning any PC with an IP address of 192.168.1.1 through 192.168.1.254) would 'know' it's on the same network as any other PC with an IP in the same range, and would not send its packet to the router. It would perform an ARP request, obtain the MAC Address of the target PC and send the packet itself.

If, on the other hand, it's preparing to send a packet to a computer with an address like 192.168.2.51 (notice the change in the third octet), it 'knows' it will have to send that to the router to be forwarded to the correct network.

So, IP Addresses are divided into a network portion and a host portion. The way the computer knows which is which (where the network portion ends and the host portion begins) is by performing an AND operation on the IP Address and the mask.

I'm pretty sure from the questions you've been asking, you've already read this somewhere. I hope I was able to clarify for you.

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I'm not sure what your question is. You're correct that the Network Number or Network ID of the address 192.168.1.50 with a 255.255.255.0 mask is 192.168.1.0. Any PC on the 192.168.1.0 subnet (meaning any PC with an IP address of 192.168.1.1 through 192.168.1.254) would 'know' it's on the same network as any other PC with an IP in the same range, and would not send its packet to the router. It would perform an ARP request, obtain the MAC Address of the target PC and send the packet itself.

If, on the other hand, it's preparing to send a packet to a computer with an address like 192.168.2.51 (notice the change in the third octet), it 'knows' it will have to send that to the router to be forwarded to the correct network.

So, IP Addresses are divided into a network portion and a host portion. The way the computer knows which is which (where the network portion ends and the host portion begins) is by performing an AND operation on the IP Address and the mask.

I'm pretty sure from the questions you've been asking, you've already read this somewhere. I hope I was able to clarify for you.

Basically what I wanted to ask was is 192.168.1.0 the network and also is 192.168.1 without the last 0 the network. In otherwords whenever you refer to the network_ID/Number you have to add the 0 on the end like this 192.168.1.0, am I correct?

And when you want to refer to the broadcast address you have to have 192.168.1.255, is this also correct?

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192.168.1.0 is the network number. 192.168.1.1 is a host on the 192.168.1.0 network.

For the rest, you're correct if using a 255.255.255.0 mask, which isn't always the case. The mask determines which is the network portion and which is the host portion of the address.

Got another question regarding subnet masks and IP addresses, thanks for your last answers... they were very useful.

Ok here it goes, if I had the address:

192.168.1.1 (Machine 1)

and

192.168.2.2(Machine 2)

And these were both using 255.255.255.0 as their subnet mask, are these on the same network?

I mean the network address of machine 1 is obviously 192.168.1.0 and the network address of machine 2 is obviously 192.168.2.0, but I still dont know if these are on the same network. Still learning, all I want to know is are these 2 machines on the same network, since the subnetmask is 255.255.255.0.

Also does anyone have some more info on advanced subnetting or intermediate subnetting, please.

Thanks In Advance.

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No, they're on separate subnets. The subnet mask of 255.255.255.0 means all of the bits in the first, second, and third octets belong to the network identification portion of the address.

If you want to learn about subnetting and networking in general, you could get some study guides for the Cisco Certified Network Associate. Even if you don't necessarily want to learn to program Cisco routers, it gives an excellent foundation in networking.

You could try a Google search for subnetting, or advanced subnetting.

You might try this site and see if it offers any new insight:

http://www.subnetonline.com/

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