240 lines
8.8 KiB
HTML
240 lines
8.8 KiB
HTML
<!--startcut ======================================================= -->
|
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
|
|
<html>
|
|
<head>
|
|
<META NAME="generator" CONTENT="lgazmail v1.1H.i">
|
|
<TITLE>The Answer Guy 37: Re: Routing and Subnetting for Classes</TITLE>
|
|
</HEAD><BODY BGCOLOR="#FFFFFF" TEXT="#000000"
|
|
LINK="#3366FF" VLINK="#A000A0">
|
|
<!-- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -->
|
|
<H4>"The Linux Gazette...<I>making Linux just a little more fun!</I>"</H4>
|
|
<P> <hr> <P>
|
|
<!-- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -->
|
|
<center>
|
|
<H1><A NAME="answer">
|
|
<img src="../../gx/dennis/qbubble.gif" alt="(?)"
|
|
border="0" align="middle">
|
|
<font color="#B03060">The Answer Guy</font>
|
|
<img src="../../gx/dennis/bbubble.gif" alt="(!)"
|
|
border="0" align="middle">
|
|
</A></H1>
|
|
<BR>
|
|
<H4>By James T. Dennis,
|
|
<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a><BR>
|
|
Starshine Technical Services,
|
|
<A HREF="http://www.starshine.org/">http://www.starshine.org/</A>
|
|
</H4>
|
|
</center>
|
|
|
|
<p><hr><p>
|
|
<!-- endcut ======================================================= -->
|
|
<!-- begin 17 -->
|
|
<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
|
|
height="50" width="60" alt="(?) " border="0"
|
|
>Re: Routing and Subnetting for Classes</H3>
|
|
|
|
|
|
<p><strong>From Faber Fedor on Thu, 07 Jan 1999
|
|
</strong></p>
|
|
<!-- ::
|
|
Re: Routing and Subnetting for Classes
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
:: -->
|
|
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
|
|
HEIGHT="28" WIDTH="50" BORDER="0"
|
|
>
|
|
Great article. I'm in the middle of teaching a TCP/IP class and
|
|
would have loved to use your article the past two days when we
|
|
were going over subnetting.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
May I have your permission to make copies and pass the article out
|
|
to my class?
|
|
</STRONG></P>
|
|
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
|
|
HEIGHT="28" WIDTH="50" BORDER="0"
|
|
>
|
|
All of my columns in the Linux Gazette are covered
|
|
under the LDP variant of the GPL. That does allow
|
|
for free distribution and use.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
You are welcome to use it however you like. Leaving
|
|
my name associated with it would be appreciated.
|
|
Then people know who to blame
|
|
<IMG SRC="../../gx/dennis/smily.gif" ALT=";)"
|
|
height="24" width="20" align="middle">.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
I'll be using a (hopefully improved) version of
|
|
this article in my book.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Note: Please also look for the article on
|
|
"proxyarp" --- this is a related subject that your
|
|
students should also understand. Some of those
|
|
concepts actually support the subnetting and routing
|
|
discussion by providing a contrast and comparison.
|
|
(As in: "Here's another way it can be done.")
|
|
</BLOCKQUOTE>
|
|
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
|
|
HEIGHT="28" WIDTH="50" BORDER="0"
|
|
>
|
|
and now, for my question: you referenced RFC1918 and "private
|
|
network addresses". I know about them, I follow them, etc. but
|
|
only because they are an RFC. I mentioned private network
|
|
addresses to a buddy of mine and he brought up the point of "Why
|
|
bother? With proxies, etc., you can have any address(es) you
|
|
want, so it doesn't matter which address(es) you choose." I can't
|
|
think of a reason to refute him.
|
|
</STRONG></P>
|
|
<P><STRONG>
|
|
So, <EM>is</EM> there a reason for choosing 192.168.x.x as opposed to
|
|
using the Post Office's 56.*.*.* for my internal network that no
|
|
one ever sees? (Yes, I know they're different classes; that's
|
|
irrelevant
|
|
<IMG SRC="../../gx/dennis/smily.gif" ALT=":-)"
|
|
height="24" width="20" align="middle">.
|
|
</STRONG></P>
|
|
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
|
|
HEIGHT="28" WIDTH="50" BORDER="0"
|
|
>
|
|
By an odd coincidence I've done some consulting for the
|
|
USPS so I am familiar with the fact that they use
|
|
proxying to "hide" their 56.*.*.* network from the
|
|
rest of the world. I suspect that about half of the
|
|
class A addresses that have been delegated are
|
|
similarly sequestered.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
It would be nice if these organizations returned their
|
|
IP addresses (exchanged them for smaller address
|
|
blocks to accomodate their publicly accessible services,
|
|
routers and proxy hosts). In the case of the USPS there
|
|
are several Class C addresses that are used by the
|
|
organization for their web sites et al.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
However, the reason for the RFC is to prevent routing
|
|
ambiguities. If the USPS decided to use some of their
|
|
56.* addresses for their websites, routers, etc ---
|
|
and you needed to access those --- your router wouldn't
|
|
have any way to know where to send these packets.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Of course, if everyone uses the same RFC1918 addresses
|
|
and we start trying to connect to one another over
|
|
VPN's then we have to do some weird "bi-directional"
|
|
masquerading and NAT (network address translation) to
|
|
turn your 10.*.*.* addresses into <EM>my</EM> 10.*.*.* addresses
|
|
and vice versa. (This is not merely a theoretical problem
|
|
--- a frient of my, has mentioned that he needs to
|
|
employ these techniques now).
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
So, the short answer is: you can do it --- but you'll
|
|
probably get bitten. There's no guarantee that the
|
|
organization who's "hidden" addresses you try to use
|
|
will continue to keep those addresses "hidden". It
|
|
shouldn't ever concern any other hosts beyond your
|
|
masquerading/NAT routers and proxy gateways --- so
|
|
long as you don't "leak" packets with these bogus
|
|
source addresses.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
This sort of "leakage" is probably the most obvious
|
|
reason to use the RFC1918 addresses. Any router
|
|
on the net can be configure to drop those packets
|
|
when any of use accidentally allow them to leak. This
|
|
is good for the whole Internet.
|
|
</BLOCKQUOTE>
|
|
<BLOCKQUOTE>
|
|
Hope that helps.
|
|
</BLOCKQUOTE>
|
|
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
|
|
HEIGHT="28" WIDTH="50" BORDER="0"
|
|
>
|
|
TIA!
|
|
Faber
|
|
</STRONG></P>
|
|
<!-- sig -->
|
|
|
|
<!-- end 17 -->
|
|
<!--startcut ======================================================= -->
|
|
<P> <hr> <P>
|
|
<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
|
|
>Copyright ©</a> 1999, James T. Dennis
|
|
<BR>Published in <I>The Linux Gazette</I> Issue 37 February 1999</H5>
|
|
<P> <hr> <P>
|
|
<!-- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -->
|
|
<P align="center">
|
|
<table width="98%"><tr valign="center" align="center">
|
|
<td rowspan="3" colspan="4"><A HREF="../lg_answer37.html"><IMG
|
|
SRC="../../gx/dennis/answernew.gif"
|
|
ALT="[ Answer Guy Index ]"></A></td>
|
|
<TD width="8%"><A HREF="./1.html">1</A></TD>
|
|
<TD width="8%"><A HREF="./2.html">2</A></TD>
|
|
<TD width="8%"><A HREF="./3.html">3</A></TD>
|
|
<TD width="8%"><A HREF="./4.html">4</A></TD>
|
|
<TD width="8%"><A HREF="./5.html">5</A></TD>
|
|
<TD width="8%"><A HREF="./6.html">6</A></TD>
|
|
<TD width="8%"><A HREF="./7.html">7</A></TD>
|
|
<TD width="8%"><A HREF="./8.html">8</A></TD>
|
|
<TD width="8%"><A HREF="./9.html">9</A></TD>
|
|
<TD width="8%"><A HREF="./10.html">10</A></TD>
|
|
|
|
</tr><tr valign="center" align="center">
|
|
<TD><A HREF="./11.html">11</A></TD>
|
|
<TD><A HREF="./12.html">12</A></TD>
|
|
<TD><A HREF="./14.html">14</A></TD>
|
|
<TD><A HREF="./15.html">15</A></TD>
|
|
<TD><A HREF="./16.html">16</A></TD>
|
|
<TD><A HREF="./17.html">17</A></TD>
|
|
<TD><A HREF="./18.html">18</A></TD>
|
|
<TD><A HREF="./19.html">19</A></TD>
|
|
<TD><A HREF="./21.html">21</A></TD>
|
|
<TD><A HREF="./22.html">22</A></TD>
|
|
|
|
</tr><tr valign="center" align="center">
|
|
<TD><A HREF="./23.html">23</A></TD>
|
|
<TD><A HREF="./28.html">28</A></TD>
|
|
<TD><A HREF="./29.html">29</A></TD>
|
|
<TD><A HREF="./30.html">30</A></TD>
|
|
<TD><A HREF="./31.html">31</A></TD>
|
|
<TD><A HREF="./32.html">32</A></TD>
|
|
<TD><A HREF="./33.html">33</A></TD>
|
|
<TD><A HREF="./34.html">34</A></TD>
|
|
<TD><A HREF="./37.html">37</A></TD>
|
|
<TD><A HREF="./38.html">38</A></TD>
|
|
|
|
</tr><tr valign="center" align="center">
|
|
<TD><A HREF="./39.html">39</A></TD>
|
|
<TD><A HREF="./41.html">41</A></TD>
|
|
<TD><A HREF="./42.html">42</A></TD>
|
|
<TD><A HREF="./43.html">43</A></TD>
|
|
<TD><A HREF="./44.html">44</A></TD>
|
|
<TD><A HREF="./45.html">45</A></TD>
|
|
<TD><A HREF="./46.html">46</A></TD>
|
|
<TD><A HREF="./47.html">47</A></TD>
|
|
<TD><A HREF="./48.html">48</A></TD>
|
|
<TD><A HREF="./49.html">49</A></TD>
|
|
|
|
</tr></table>
|
|
</P>
|
|
<P> <hr> <P>
|
|
<!-- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -->
|
|
<P> <hr> <P>
|
|
<!-- begin lgnav ::::::::::::::::::::::::::::::::::::::::::::::::::: -->
|
|
<A HREF="../index.html"
|
|
><IMG SRC="../../gx/indexnew.gif" ALT="[ Table Of Contents ]"></A>
|
|
<A HREF="../../index.html"
|
|
><IMG SRC="../../gx/homenew.gif" ALT="[ Front Page ]"></A>
|
|
<A HREF="../lg_bytes37.html"
|
|
><IMG SRC="../../gx/back2.gif" ALT="[ Previous Section ]"></A>
|
|
<A HREF="../york.html"
|
|
><IMG SRC="../../gx/fwd.gif" ALT="[ Next Section ]"></A>
|
|
<!-- end lgnav ::::::::::::::::::::::::::::::::::::::::::::::::::::: -->
|
|
<!-- ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -->
|
|
</BODY></HTML>
|
|
<!--endcut ========================================================= -->
|