I am learning to handle iptables when but I had to port forward over a NAT host machine to a server on a VM running CentOS 6.9. Host machine is running Kubuntu 18.04.

After trying some iptable rules and ufw (which I promptly disabled after), yum on the VM insists on picking ipv6 mirrors. I have tried new VMs but it still doesn't work.

I installed iptables-persistent on host and despite running sudo iptables -F it seems that the rules are not flushed from /etc/iptable/rules.v4 Now I am worried if deleting the entire file would result in instability with my host machine and doesn't solve it at all.

2 Answers 2


I solved the issue by uninstalling iptables-persistent from the host machine and restarting the machine. One of the rules that I have added while experimenting must have tampered with the access. I have also deleted /etc/iptables/rules.v4


YUM seems to prefer IPv6 over IPv4 when the former is available. You can set


in [main] section of /etc/yum.conf to force resolution to only try IPv4 (A-records).

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