iptables -t filter -F
iptables -t filter -A INPUT -m state --state ESTABLISHED -j ACCEPT
iptables -t filter -A INPUT -i lo -j ACCEPT
iptables -t filter -A INPUT -p icmp -j ACCEPT
iptables -t filter -A INPUT -p tcp -m tcp -m multiport --dports 53,26 -m state --state NEW -j ACCEPT
iptables -t filter -A INPUT -p udp -m tcp -m multiport --dports 53,26 -m state --state NEW -j ACCEPT
iptables -t filter -A INPUT -i eth0 -j ACCEPT
iptables -t filter -A INPUT -i ppp0 -p udp -m udp --sport 53 -j ACCEPT
iptables -t filter -A INPUT -p tcp -m tcp --dport 53 -j ACCEPT
iptables -t filter -A INPUT -i ppp0 -p udp -m udp --sport 26 -j ACCEPT
iptables -t filter -A INPUT -p tcp -m tcp --dport 26 -j ACCEPT
iptables -t filter -A FORWARD -o ppp0 -p tcp -m tcp --tcp-flags SYN,RST SYN -m tcpmss --mss 1400:1536 -j TCPMSS --clamp-mss-to-pmtu
iptables -t filter -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -t filter -A FORWARD -p icmp -j ACCEPT
iptables -t filter -A FORWARD -i eth0 -o ppp0 -m state --state NEW -j ACCEPT
iptables -t filter -A OUTPUT -m state --state ESTABLISHED -j ACCEPT
iptables -t filter -A OUTPUT -o lo -j ACCEPT
iptables -t filter -A OUTPUT -o eth0 -j ACCEPT
iptables -t filter -A OUTPUT -p icmp -j ACCEPT
iptables -t filter -A OUTPUT -p tcp -m tcp -m multiport --dports 53,26 -m state --state NEW -j ACCEPT
iptables -t filter -A OUTPUT -p udp -m tcp -m multiport --dports 53,26 -m state --state NEW -j ACCEPT
iptables -P FORWARD ACCEPT
iptables -t nat -A PREROUTING -i ppp0 -p tcp --dport 26 -j DNAT --to-destination 192.168.1.200
iptables -t nat -A PREROUTING -i ppp0 -p tcp --dport 53 -j DNAT --to-destination 192.168.1.200

iptables -t nat -A PREROUTING -i ppp0 -p udp --dport 26 -j DNAT --to-destination 192.168.1.200
iptables -t nat -A PREROUTING -i ppp0 -p udp --dport 53 -j DNAT --to-destination 192.168.1.200