show interfaces in iptables -L

Add -v for the verbose mode.

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
39050 4448K ACCEPT     all  --  lo     *       0.0.0.0/0            0.0.0.0/0           
 6595  544K ACCEPT     icmp --  *      *       0.0.0.0/0            0.0.0.0/0           
  419 15084 ACCEPT     2    --  *      *       0.0.0.0/0            0.0.0.0/0           

Even better, change the command to -S for plain mode:

-P INPUT ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -p igmp -j ACCEPT