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Home > Archive > alt.certification.network-plus > November 2003 > Making sense of SUBNETS
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Making sense of SUBNETS
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| Howdy everyone,
I am having a rough time understanding subnet. I am already Network+
certified but I just need some clarification.
First, I understand what subnetting is, and I can calculate subnet masks and
such. What I don't undestand, is how a machine outside your local network
gets your subnet mask, or calculates the right address.
For example; I personally use DSL with a static IP address. I was given a
Subnet IP address with a subnet mask. How do machines accessing mine (from
accross the internet) determine the subnet mask or how are they able to
address my machine (If I don't contact them first)?
Maybe a good tutorial on subnetting is all I need. I haven't been able to
find much which seems to answer my question, though.
Thanks
- Mark
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| Charles M. Kozierok 2003-11-23, 2:25 pm |
| In article <k87wb.10668$sb4.3407@newsread2.news.pas.earthlink.net>,
Mark <markohl@earthlink.net> wrote:
} Howdy everyone,
}
} I am having a rough time understanding subnet. I am already Network+
} certified but I just need some clarification.
}
} First, I understand what subnetting is, and I can calculate subnet masks and
} such. What I don't undestand, is how a machine outside your local network
} gets your subnet mask, or calculates the right address.
Unless I misunderstand your question.. the answer is that they don't
need to know your subnet mask. The mask is used by your machine to
determine whether to send on the local network or not; remote devices
know from your IP address and their own subnet mask that your machine is
external to them and the routers take care of the rest. (Massively
simplified.)
peace,
-*-
charles
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| FireSword 2003-11-23, 4:25 pm |
| Charles answered your question.
the subnet mask is not needed part of the ip packets and is not needed to
get a packet to its destination.
A piece of advise:
Saying in a newsgroup that you use a static IP address is the same as giving
away your IP.
So if you don't have a very good firewall already, go buy one.
"Mark" <markohl@earthlink.net> wrote in message
news:k87wb.10668$sb4.3407@newsread2.news.pas.earthlink.net...
> Howdy everyone,
>
> I am having a rough time understanding subnet. I am already Network+
> certified but I just need some clarification.
>
> First, I understand what subnetting is, and I can calculate subnet masks
and
> such. What I don't undestand, is how a machine outside your local network
> gets your subnet mask, or calculates the right address.
>
> For example; I personally use DSL with a static IP address. I was given a
> Subnet IP address with a subnet mask. How do machines accessing mine
(from
> accross the internet) determine the subnet mask or how are they able to
> address my machine (If I don't contact them first)?
>
> Maybe a good tutorial on subnetting is all I need. I haven't been able to
> find much which seems to answer my question, though.
>
> Thanks
>
> - Mark
>
>
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| Frederic 2003-11-23, 6:25 pm |
| Tutorials:
http://www.ralphb.net/IPSubnet/index.html
http://www.learntosubnet.com/
--
Frederic
MCP, IT Project+, i-Net+, CIWA, A+
member of: CompTIA-ITPRO, HDI, IETF
------------------------------------------------------
http://fredsfastcram.netfirms.com
------------------------------------------------------
"Mark" <markohl@earthlink.net> wrote in message
news:k87wb.10668$sb4.3407@newsread2.news.pas.earthlink.net...
> Howdy everyone,
>
> I am having a rough time understanding subnet. I am already Network+
> certified but I just need some clarification.
>
> First, I understand what subnetting is, and I can calculate subnet masks
and
> such. What I don't undestand, is how a machine outside your local network
> gets your subnet mask, or calculates the right address.
>
> For example; I personally use DSL with a static IP address. I was given a
> Subnet IP address with a subnet mask. How do machines accessing mine
(from
> accross the internet) determine the subnet mask or how are they able to
> address my machine (If I don't contact them first)?
>
> Maybe a good tutorial on subnetting is all I need. I haven't been able to
> find much which seems to answer my question, though.
>
> Thanks
>
> - Mark
>
>
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