How to assign a second IP address to one Ethernet port

[Anonymous]

I did a clean install of Mac OS X Server 10.3 on my Grape 266MHz iMac (what? Why are you looking at me like that?). Before I used IPNetShareX to allow NAT via the single 10/100 Ethernet port. For some reason, this does not seem to function under 10.3 Server (don’t know about 10.3 client). After some digging I came up with a soultion. If you open the file [b:5cbf4a815d]/System/Library/StartupItems/IPAliases/IPAliases[/b:5cbf4a815d], you’ll find at the top:

[code:1:5cbf4a815d]
#!/bin/sh
. /etc/rc.common

##
# /System/Library/StartupItems/IPAliases/IPAliases: Start up IP aliasing.
##
# This script will add IP aliases to existing interface(s)
#
# This script utilizes the file /etc/IPAliases.conf to determine what, if any
# IP aliases need to be defined for a given network interface. The format
# of the file /etc/IPAliases.conf is very strict. Entries must be in the form
# of:
#
# interface:ipaddress[:netmask]
#
# See the IPAliases.conf(5) man page for further information.
#
[/code:1:5cbf4a815d]

So, too assign another IP address to an Ethernet port create the file [b:5cbf4a815d] /etc/IPAliases.conf[/b:5cbf4a815d] and add the line

[code:1:5cbf4a815d] interface:ipaddress[:netmask][/code:1:5cbf4a815d]

for example, to assign 192.168.2.1 to your primary Ethernet interface you would add the line

[code:1:5cbf4a815d]en0:192.168.2.1:255.255.255.0[/code:1:5cbf4a815d]

Pretty nifty, huh?

skinlayers[/code][/b]

[Anonymous]

I initially tried creating a seccond interface in the 10.3 GUI, but the NAT setting weren’t getting applied unless I stopped and restarted NAT after booting. Using this method allows me to NAT through my single ethernet port.

[Author]

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