Author Topic: Basic Networking Question  (Read 1255 times)

Offline mbaldw

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Basic Networking Question
« on: Jan 15, 2009, 01:13 AM »

Offline Buffalo2102

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Re: Basic Networking Question
« Reply #1 on: Jan 15, 2009, 04:02 AM »
It is perfectly possible to share files and printers between workgroups but it can be prone to errors/problems.  It is always best to have all PC's on a LAN belonging to the same workgroup but it is not essential.

File and printer sharing and the whole Domain/Workgroup malarky is handled by Windows whereas the ping command is a very low-level (layer 2) command and is not related to Windows, workgroups etc. at all.  I suspect that the reason you can't ping other PC's is down to firewall settings or some other network issue.

Buff.
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Offline mbaldw

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Re: Basic Networking Question
« Reply #2 on: Jan 16, 2009, 12:41 AM »
Spot on, Buff!   It transpires that it was a firewall-related issue.   Curiously, despite adding the network to my firewall's 'trusted' zone manually, it took me repeating the action through the automated wizard for it to work.   Anyway, they're now pinging as they should.   Thanks for the help and explanation.   I presume, incidentally, that the ping is also independent of subnet masks and the like and you should be able to ping any other IP address on a network, regardless of it's subnet, default gateway etc.?

Cheers,
Marc.

Offline Buffalo2102

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Re: Basic Networking Question
« Reply #3 on: Jan 16, 2009, 01:54 PM »
Sorry, there was a typo in my previous post - I meant to say layer 3, not 2 (although you can ping at layer 2 also).  ICMP ping is still totally independent of Workgroups etc.

However, it is not independent of subnet masks as you presume.  It is the subnet mask that defines the boundaries of the immediate network and you can only ping other IP addresses that are within the IP address range defined by the subnet mask.  Unless, you have a routing device that joins 2 networks and is able to route traffic between them.



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Offline mbaldw

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Re: Basic Networking Question
« Reply #4 on: Jan 20, 2009, 04:32 AM »
Thanks Buff, I think I understand this a little better now.   My final query on this actually relates to the subnets themselves.   Although as I have a home network subnetting isn't really of importance to me I am curious about something.

I've read several comments on the subject to suggest you can split, say a Class C network, in two by creating a subnet mask of 255.255.255.128, which would group IP addresses into 192.168.1.1 - 192.168.1.127 (Network A) and then 192.168.1.129 - 192.168.1.255 (Network B).   Assuming this is carrect, how would you input the subnet mast into the TCP/IP settings?   Would all PCs assigned IP addresses within Network A have the subnet mastk 255.255.255.1 and the ones in Network B have 255.255.255.128, or does it work differently to that?

Cheers,
Marc.

Offline Buffalo2102

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Re: Basic Networking Question
« Reply #5 on: Jan 21, 2009, 01:22 AM »
No, it doesn't work like that.  Both networks would have a 255.255.255.128 subnet mask.

If you want to understand how it works, you have to convert things to 8-bit binary.  The subnet mask 255.255.255.128 in binary is -

128 64 32 16 8 4 2 1     128 64 32 16 8 4 2 1     128 64 32 16 8 4 2 1     128 64 32 16 8 4 2 1
  1   1   1   1  1 1 1 1       1   1   1  1  1 1 1 1        1   1   1  1  1 1 1 1        1   0   0   0 0 0 0 0

So the subnet mask 11111111-11111111-11111111-10000000 is telling us that the first 3 octets and the first bit of the last octet are the network address for this network and the last 7 bits are used for the host addresses.

If you apply that to a IP address of 192.168.1.1, you get -

                 128 64 32 16 8 4 2 1      128 64 32 16 8 4 2 1     128 64 32 16 8 4 2 1     128 64 32 16 8 4 2 1
Subnet        1   1   1   1  1 1 1 1        1   1   1  1  1 1 1 1        1   1   1  1  1 1 1 1        1   0   0   0 0 0 0 0
IP address   1   1   0   0  0 0 0 0        1   0   1  0  1 0 0 0        0   0   0  0  0 0 0 1        0   0   0   0 0 0 0 1

We can see that the network address for this IP address is 11000000-10101000-00000001-0-------

Since the last bit of this address is the bit that corresponds to 128 in the last octet, the network address will stay the same for all IP addresses in this range up to 192.168.1.128.  At this point, the bit that corresponds to 128 in the last octet changes to become a 1 instead of a zero (so 11000000-10101000-00000001-1-------) and this will be the same for all of the higher IP addresses in the range.  Therefore, this range will be seen as a different network but the subnet mask for both networks will be the same.  The range of the network is a function of both the IP address and the subnet mask.

Not sure if that made things any clearer for you but there are probably far better explanations elsewhere on the web.

Cheers

Buff

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Offline mbaldw

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Re: Basic Networking Question
« Reply #6 on: Jan 22, 2009, 11:36 AM »
Thanks for taking the time to explain that, Buff.   I think I understand it now.

Cheers,
Marc.

Offline Buffalo2102

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Re: Basic Networking Question
« Reply #7 on: Jan 23, 2009, 03:45 AM »
No worries.

Your question turned out to be not so basic after all. ;D

Buff
Vista x64 Home Premium. Intel Core 2 Duo E8400 Abit IP35, 4 Gig Kingston HyperX PC8500C5 DDR2, GTX260, Creative X-Fi Extreme Gamer, Antec 900 Gaming Case.