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lightxx
Asked: 2016-06-23 00:01:09 +0800 CST

DHCPv6 not working when UFW is enabled (Ubuntu 16.04 LTS)

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So, as the title says, I setup a isc-dhcp-server for DHCPv6, which is working as long as UFW is disabled.

Once enabled, though I have all the necessary rules in place, and UFW is enabled for v6, it stops working.

My rules are:

xxx@deadpool:/etc/ufw# grep '546\|547' *
after6.rules:-A ufw6-after-input -p udp --dport 546 -j ufw6-skip-to-policy-input
after6.rules:-A ufw6-after-input -p udp --dport 547 -j ufw6-skip-to-policy-input    
before6.rules:-A ufw6-before-input -p udp -s fe80::/10 --sport 547 -d fe80::/10 --dport 546 -j ACCEPT

I found two related but fixed bugs on launchpad: https://bugs.launchpad.net/ubuntu/+source/ufw/+bug/947416 https://bugs.launchpad.net/ubuntu/+source/ufw/+bug/1007326

Any ideas?

ubuntu ufw isc-dhcp dhcpv6

2 Answers

  1. I see an existing rule for a DHCP client:

    # allow dhcp client to work
-A ufw6-before-input -p udp -s fe80::/10 --sport 547 -d fe80::/10 --dport 546 -j ACCEPT

    I think you need to reverse the source/destination ports for your *server:

    # dhcp server
-A ufw6-before-input -p udp -s fe00::/7 --sport 546 -d fe00::/7 --dport 547 -j ACCEPT
    • 2

  2. Change it to fe00::/7, you have to allow IPv6 multicast addresses as well. Your server should be listening on ff05::1:3 and ff02::1:2.

    See: https://en.wikipedia.org/wiki/Multicast_address#IPv6

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