http://www.freebsd.org/doc/ru/books/handbook/config-network-setup.html

$ ifconfig

# dhclient em0

# ifconfig em0 inet 172.16.1.X/24

# ifconfig em0 inet 10.N.Z.M/24 alias

# ifconfig em0 -alias

# route -n flush

# route add default 172.16.1.254

# route add 192.168.X/24 172.16.1.X

# hostname server.corpX.un
  или
# sysctl kern.hostname=server.corpX.un

# ifconfig em0

# arp -an

# arp -a -d

# netstat -rn -f inet

# netstat -I em0 -inb

# netstat -I em0 -inb -w 1

# ping 8.8.8.8

# traceroute -n 8.8.8.8

# sockstat -4

# cat /etc/rc.conf

hostname="server.corpX.un"

ifconfig_em0="inet 172.16.1.X/24"
defaultrouter="172.16.1.254"

### Rename interface example ###
# ifconfig_em0_name=wan0
# ifconfig_wan0="inet 172.16.1.X/24"

### Alias example ###
# ifconfig_em0_alias0="inet 192.168.1.10/24"
# ifconfig_em0_alias1="inet 172.16.1.200+X/32"
# ifconfig_em0_alias2="inet 10.5.Z.X/24"

### 802.1q example ###
# cloned_interfaces="vlan2 vlan3"
# ifconfig_vlan2="inet 172.16.2.X/24 vlan 2 vlandev em0"
# ifconfig_vlan3="inet 172.16.3.X/24 vlan 3 vlandev em0"

### UP iface without ip example ###
# ifconfig_em0="up"

### Bridge example ###
# cloned_interfaces="bridge0"
# ifconfig_bridge0="addm em0 addm em1 up"
# ifconfig_em0="dhcp"
# ifconfig_em1="up"

# /etc/rc.d/hostname start
# /etc/rc.d/netif start
# /etc/rc.d/routing start

или

# service hostname start
# service netif start
# service routing start

# cat /etc/hosts

127.0.0.1       localhost localhost.corpX.un

172.16.1.X	server.corpX.un server

# cat /etc/resolv.conf

domain  corpX.un
nameserver      172.16.1.254

# cat /etc/rc.conf

hostname="client1"

ifconfig_em0="DHCP"

# cat /etc/hosts

127.0.0.1     localhost

# :> /etc/resolv.conf