How to simulate different NAT behaviours

Question

I am working on Holepunching using UDP and UDT. For the final testing I need to test the application on different NAT types (Symmetric,full cone,restricted cone, port restricted NATs).

Is there any method I can simulate these? What I expect here is some kind of virtual-Box setup. Can I use PC as a router so that I can configure according to my needs?

In general how do we test applications for different network conditions?

Answer 1

Just in case someone else is looking to do this, this website explains how to set up the different NAT environments using IPTables.

Update

It has been a few years since I did this, given that the link was placed behind a login, and the rewind was also placed behind a login, I went through my notes from back than and found the following. Please note these are untested.

Full Cone NAT;

iptables -t nat -A POSTROUTING -o eth1 -j SNAT --to-source "public IP"
iptables -t nat -A PREROUTING -i eth1 -j DNAT --to-destination "private IP"

Restricted Cone NAT;

iptables -t nat -A POSTROUTING -o eth1 -p udp -j SNAT --to-source "public IP"
iptables -t nat -A PREROUTING -i eth1 -p udp -j DNAT --to-destination "private IP"
iptables -A INPUT -i eth1 -p udp -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -i eth1 -p udp -m state --state NEW -j DROP

Port Restricted Cone NAT;

iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to-source "public IP"

Symmetric NAT;

echo "1" >/proc/sys/net/ipv4/ip_forward
iptables --flush
iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE --random
iptables -A FORWARD -i eth1 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT