How to assign an additional IP address (alias) to a network interface in FreeBSD

To set up an additional network alias in FreeBSD (it will disappear after reboot):

ifconfig em0 alias 1.2.3.4/24

To remove an alias:

ifconfig em0 -alias 1.2.3.4/24

To assign persistent IP aliases edit /etc/rc.conf:

ifconfig_em0_alias0= "inet 1.2.3.4 netmask 255.255.255.0"
ifconfig_em0_alias1= "inet 1.2.3.5 netmask 255.255.255.0"

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