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>Setting up IP Aliasing on A Linux Machine Mini-HOWTO</TH
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><A
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>2. Commands</A
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><P
>Load the IP Alias module (you can skip this step if you compiled
the module into the kernel):</P
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>/sbin/insmod /lib/modules/`uname -r`/ipv4/ip_alias.o</PRE
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><P
>Setup the loopback, eth0, and all the IP addresses beginning with the
main IP address for the eth0 interface:</P
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>/sbin/ifconfig lo 127.0.0.1
/sbin/ifconfig eth0 up
/sbin/ifconfig eth0 172.16.3.1
/sbin/ifconfig eth0:0 172.16.3.10
/sbin/ifconfig eth0:1 172.16.3.100</PRE
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><P
>172.16.3.1 is the main IP address, while .10 and .100 are the aliases. The
magic is the eth0:x where x=0,1,2,...n for the different IP addresses. The
main IP address does not need to be aliased.</P
></LI
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><P
>Setup the routes. First route the loopback, then the net, and
finally, the various IP addresses starting with the default (originally
allocated) one:</P
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>/sbin/route add -net 127.0.0.0
/sbin/route add -net 172.16.3.0 dev eth0
/sbin/route add -host 172.16.3.1 dev eth0
/sbin/route add -host 172.16.3.10 dev eth0:0
/sbin/route add -host 172.16.3.100 dev eth0:1
/sbin/route add default gw 172.16.3.200</PRE
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><P
>That's it.</P
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><P
>In the example IP address above, I am using the Private IP addresses (RFC 1918) for
illustrative purposes. Substitute them with your own official or private IP
addresses.</P
><P
>The example shows only 3 IP addresses. The max is defined to be 256 in
<TT
CLASS="FILENAME"
>/usr/include/linux/net_alias.h.</TT
> 256 IP addresses on ONE card is a lot :-)!</P
><P
>Here's what my <TT
CLASS="FILENAME"
>/sbin/ifconfig</TT
> looks like:</P
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CLASS="PROGRAMLISTING"
>lo Link encap:Local Loopback
inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0
UP BROADCAST LOOPBACK RUNNING MTU:3584 Metric:1
RX packets:5088 errors:0 dropped:0 overruns:0
TX packets:5088 errors:0 dropped:0 overruns:0
eth0 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20
inet addr:172.16.3.1 Bcast:172.16.3.255 Mask:255.255.255.0
UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1
RX packets:334036 errors:0 dropped:0 overruns:0
TX packets:11605 errors:0 dropped:0 overruns:0
Interrupt:7 Base address:0x378
eth0:0 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20
inet addr:172.16.3.10 Bcast:172.16.3.255 Mask:255.255.255.0
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0
TX packets:0 errors:0 dropped:0 overruns:0
eth0:1 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20
inet addr:172.16.3.100 Bcast:172.16.3.255 Mask:255.255.255.0
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:1 errors:0 dropped:0 overruns:0
TX packets:0 errors:0 dropped:0 overruns:0</PRE
></TD
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><P
>And <TT
CLASS="FILENAME"
>/proc/net/aliases</TT
>:</P
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><PRE
CLASS="SCREEN"
>device family address
eth0:0 2 172.16.3.10
eth0:1 2 172.16.3.100</PRE
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><P
>And <TT
CLASS="FILENAME"
>/proc/net/alias_types</TT
>: </P
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><PRE
CLASS="PROGRAMLISTING"
>type name n_attach
2 ip 2</PRE
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><P
>Of course, the stuff in <TT
CLASS="FILENAME"
>/proc/net</TT
> was created by the <B
CLASS="COMMAND"
>ifconfig</B
> command and
not by hand!</P
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