root@controller31:~# iptables -n -L -t nat --line-number
Chain PREROUTING (policy ACCEPT)
num target prot opt source destination
1 DNAT tcp -- 0.0.0.0/0 192.168.2.31 tcp dpt:21 to:192.168.2.32
2 DNAT tcp -- 0.0.0.0/0 192.168.2.32 tcp dpt:21 to:192.168.2.31
Chain INPUT (policy ACCEPT)
num target prot opt source destination
Chain OUTPUT (policy ACCEPT)
num target prot opt source destination
Chain POSTROUTING (policy ACCEPT)
num target prot opt source destination
root@controller31:~# iptables -D PREROUTING 2
iptables: No chain/target/match by that name.
root@controller31:~# iptables -t nat -D PREROUTING 2
root@controller31:~# iptables -t nat -D PREROUTING 1