Правила для IPTABLES.
# разрешаем icmp пакеты через vpn
# (необходимо для пинга)
$ip -A INPUT -p icmp -m icmp -i $VPN_IFACE --icmp-type echo-request -j ACCEPT
$ip -A OUTPUT -p icmp -m icmp -o $VPN_IFACE --icmp-type echo-request -j ACCEPT
$ip -A FORWARD -p icmp -m icmp -i $VPN_IFACE -o $LAN_IFACE --icmp-type echo-request -j ACCEPT
$ip -A FORWARD -p icmp -m icmp -o $VPN_IFACE -i $LAN_IFACE --icmp-type echo-request -j ACCEPT
$ip -A INPUT -p icmp -m icmp -i $VPN_IFACE --icmp-type echo-reply -j ACCEPT
$ip -A OUTPUT -p icmp -m icmp -o $VPN_IFACE --icmp-type echo-reply -j ACCEPT
$ip -A FORWARD -p icmp -m icmp -i $VPN_IFACE -o $LAN_IFACE --icmp-type echo-reply -j ACCEPT
$ip -A FORWARD -p icmp -m icmp -o $VPN_IFACE -i $LAN_IFACE --icmp-type echo-reply -j ACCEPT