Yes you can, if the ip_alias module is compiled. You could use something like 'ifconfig eth0:0 10.10.0.50 netmask 255.255.0.0 up' 'ifconfig eth0:1 10.10.0.51 netmask 255.255.0.0 up'
Most versions of Unix support hardware virtual IP address' The ones I know for sure are Solaris, HP-UX and I am fairly sure Linux does as well. The easiest way to extend your interface into multiple IP's is by using the ifconfig command and appending :0 to the device name ie eth0 to eth0:0 or hme0 to hme0:0 and so on. This configures the device while the system is running, but a reboot will make the configuration disappear. To ensure the new IP's remain after reboot each systems is different. For Solaris you can add the IP Address in a text file under the /etc directory called hostname.<interface_name> eg hostname.hme0:1 HP has a boot file that it sources during boot time (it's been awhile) and I'm not sure for Linux. The easy way would beto install webmin and modify it using it. This tool would allow you to make the changes and make them permanent.
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How unix support multiple ip address
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