iptables – source host not found

If you see something like:

iptables v1.4.21: host/network `proxy.ovh.net' not found 
Try `iptables -h' or 'iptables --help' for more information. 
iptables v1.4.21: host/network `proxy.p19.ovh.net' not found 
Try `iptables -h' or 'iptables --help' for more information. 
iptables v1.4.21: host/network `proxy.rbx.ovh.net' not found 
Try `iptables -h' or 'iptables --help' for more information. 
iptables v1.4.21: host/network `proxy.sbg.ovh.net' not found 
Try `iptables -h' or 'iptables --help' for more information. 
iptables v1.4.21: host/network `proxy.bhs.ovh.net' not found 
Try `iptables -h' or 'iptables --help' for more information. 
iptables v1.4.21: host/network `ping.ovh.net' not found 
Try `iptables -h' or 'iptables --help' for more information.

Authorize your DNS traffic before :

# ...
# DNS 
/sbin/iptables -t filter -A OUTPUT -p tcp --dport 53 -j ACCEPT 
/sbin/iptables -t filter -A OUTPUT -p udp --dport 53 -j ACCEPT 
/sbin/iptables -t filter -A INPUT -p tcp --dport 53 -j ACCEPT 
/sbin/iptables -t filter -A INPUT -p udp --dport 53 -j ACCEPT 
/sbin/iptables -A INPUT -i eth0 -p icmp --source proxy.ovh.net -j ACCEPT
/sbin/iptables -A INPUT -i eth0 -p icmp --source proxy.p19.ovh.net -j ACCEPT 
/sbin/iptables -A INPUT -i eth0 -p icmp --source proxy.rbx.ovh.net -j ACCEPT 
/sbin/iptables -A INPUT -i eth0 -p icmp --source proxy.sbg.ovh.net -j ACCEPT 
/sbin/iptables -A INPUT -i eth0 -p icmp --source proxy.bhs.ovh.net -j ACCEPT
# ...