root@open:~# sudo iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
root@open:~# iptables-save
# Generated by iptables-save v1.4.14 on Thu May 30 19:02:39 2013
*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
-A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
COMMIT
# Completed on Thu May 30 19:02:39 2013
# Generated by iptables-save v1.4.14 on Thu May 30 19:02:39 2013
*filter
:INPUT ACCEPT [144:11234]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [145:16292]
COMMIT
# Completed on Thu May 30 19:02:39 2013
root@open:~# iptables --list
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
root@open:~# sudo iptables-save
# Generated by iptables-save v1.4.14 on Thu May 30 19:02:59 2013
*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [1:66]
:POSTROUTING ACCEPT [1:66]
-A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
-A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
COMMIT
# Completed on Thu May 30 19:02:59 2013
# Generated by iptables-save v1.4.14 on Thu May 30 19:02:59 2013
*filter
:INPUT ACCEPT [205:15732]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [203:24313]
COMMIT
# Completed on Thu May 30 19:02:59 2013
root@open:~# iptables --list
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
root@open:~# sudo iptables --list
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination