206 lines
4.2 KiB
HTML
206 lines
4.2 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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>Assigning Private Network IP Addresses to the Internal LAN</TITLE
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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TITLE="Setting Up IP Masquerade"
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>Linux IP Masquerade HOWTO</TH
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>Chapter 3. Setting Up IP Masquerade</TD
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><A
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NAME="ADDRESSING-THE-LAN"
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>3.3. Assigning Private Network IP Addresses to the Internal LAN</H1
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><P
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>Since all <STRONG
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>INTERNAL MASQed</STRONG
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> machines should
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NOT have official Internet assigned addressees, there must be a specific and
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accepted way to allocate addresses to those machines without conflicting with
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anyone else's Internet address. </P
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><P
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>From the original IP Masquerade FAQ:</P
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><P
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><A
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HREF="http://www.cis.ohio-state.edu/cgi-bin/rfc/INDEX.rfc.html"
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TARGET="_top"
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>RFC
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1918</A
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> is the official document on which IP addresses are to be used in
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a non-connected or "private" network. There are 3 blocks of numbers set aside
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specifically for this purpose.</P
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><P
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BGCOLOR="#E0E0E0"
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="SCREEN"
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>Section 3: Private Address Space
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The Internet Assigned Numbers Authority (IANA) has reserved the
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following three blocks of the IP address space for private networks:
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10.0.0.0 - 10.255.255.255
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172.16.0.0 - 172.31.255.255
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192.168.0.0 - 192.168.255.255
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We will refer to the first block as "24-bit block", the second as "20-bit
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block", and the third as "16-bit" block". Note that the first block is
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nothing but a single class A network number, while the second block is a set
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of 16 continuous class B network numbers, and the third block is a set of 255
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continuous class C network numbers.</PRE
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></FONT
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></P
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><P
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>For the record, my preference is to use the 192.168.0.0 network with a
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255.255.255.0 Class-C subnet mask and thus this HOWTO reflects this. Any of
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the above private networks are valid, but just be SURE to use the correct
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subnet-mask.</P
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><P
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>So, if you're using a Class-C network, you should number your TCP/IP enabled
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machines as 192.168.0.1, 192.168.0.2, 192.168.0.3, .., 192.168.0.x </P
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><P
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>192.168.0.1 is usually set as the internal gateway or Linux MASQ machine which
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reaches the external network. Please note that 192.168.0.0 and 192.168.0.255
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are the Network and Broadcast address respectively (these addresses are
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RESERVED). Avoid using these addresses on your machines or your network will
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not function properly. </P
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VALIGN="top"
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>Checking your existing kernel for MASQ functionality</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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>Configuring IP Forwarding Policies</TD
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