It is possible to create network alias or assign 2 ip address to a single NIC under FreeBSD operating system.
Sample setup:
=> lnc0 - IP : 192.168.1.1/255.255.255.0
=>lnc0 alias - IP : 192.168.1.5/255.255.255.255
Note: Netmask must be diffrent otherwise you will get an error ifconfig: ioctl (SIOCAIFADDR): File exists
Set ip alias using ifconfig command line utility
Login as the root user.
Now, use ifconfig command as follows to set alias:
# ifconfig lnc0 192.168.1.5 netmask 255.255.255.255 alias
Persistent IP Alias Configuration
Edit file /etc/rc.conf to setup persistent ip aliasing option by appending following configuration, so that next time FreeBSD comes up (after restart/shutdown) it will create alias for you:
ifconfig_lnc0_alias0=”192.168.1.5 netmask 255.255.255.255″
Finally, < href=”http://www.cyberciti.biz/tips/freebsd-how-to-start-restart-stop-network-service.html”>Restart FreeBSD network service using network restart script:
# /etc/rc.d/netif restart && /etc/rc.d/routing restart
Display alias and real ip using ifconfig lnc0 command:
# ifconfig lnc0
Sample output:
lnc0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet6 fe80::20c:29ff:fe01:ddbd%lnc0 prefixlen 64 scopeid 0×1
inet 192.168.1.2 netmask 0xffffff00 broadcast 192.168.1.255
inet 192.168.1.5 netmask 0xffff
Sample /etc/rc.conf file with IP aliasing
Here is my /etc/rc.conf file with em0 and em1 interface with 5 aliases:
hostname=”sun.nixcraft.in”
# default vsnl router interface
defaultrouter=”202.54.1.200″
# Force 10Mbps for both public and private LAN interace
ifconfig_em0=”inet 10.20.110.2 netmask 255.255.255.192 media 10baseT/UTP mediaopt full-duplex”
ifconfig_em1=”inet 202.52.1.2 netmask 255.255.255.248 media 10baseT/UTP mediaopt full-duplex”
ifconfig_em0_alias0=”inet 10.20.1.226 netmask 255.255.255.0″
ifconfig_em0_alias1=”inet 10.20.1.227 netmask 255.255.255.0″
ifconfig_em0_alias2=”inet 10.20.1.228 netmask 255.255.255.0″
ifconfig_em0_alias3=”inet 10.20.1.229 netmask 255.255.255.0″
ifconfig_em0_alias4=”inet 10.20.1.230 netmask 255.255.255.0″
# static routing configuration
static_routes=”lan0″
route_lan0=”-net 10.0.0.0/8 10.20.110.1″
ref : http://www.cyberciti.biz/tips/freebsd-how-to-setup-2-ip-address-on-one-nic.html