The Problem

My syslog shows:

dhclient[24931]: send_packet6: Operation not permitted
dhclient[24931]: dhc6: send_packet6() sent -1 of 56 bytes
dhclient[367]: XMT: Solicit on eth0, interval 122930ms.
dhclient[367]: send_packet6: Operation not permitted
dhclient[367]: dhc6: send_packet6() sent -1 of 56 bytes

The Cause

DHCP for IPv6 uses different ports than IPv4, so your IPTABLES / CSF firewall may need to have its rules adjusted if you start using IPv6.

The Solution

Set your firewall to allow UDP in/out for:
IPv4: 67,68
IPv6: 546,547

That’s it. The error is gone.

Robbie // The Bald Nerd