Do I need to use ip6tables in addition to iptables?
 

I noticed when I did 'sudo service ip6tables status' on a couple of my CentOS machines, they have ip6tables up and running. I'm wondering under what circumstances I need to keep them enabled, and if so whether I need to ensure I have the right rules for ip6tables as I've been trying to for regular iptables. I'm pretty new to networking so I'm really not sure if/when I need to use ip6tables... Any guidance for me here would be wonderful.

if you are running or using ipv6 on your network then you will need ip6tables, if you're not running then I suppose you better disable it, just an opinion. It's your call to decide.