Default security functions on an IPv6 CPE

Mikael Abrahamsson swmike at
Thu May 12 10:54:32 CEST 2011

On Thu, 12 May 2011, Ted Mittelstaedt wrote:

We had an argument here at the office regarding firewall in CPE, and my 
opinion was that since UNPNv6 isn't really supported anywhere, IPv6 with 
deny new sessions might even be worse in practice than NAT44 with UPNP. It 
seems Windows 7 does support UPNPv6, but I have yet to locate information 
regarding support in shipping software for IPv6 enabled CPEs.

So I would like to withdraw my recommendation before about low-ports 
closed but high-ports open. I now believe that it's better to have a 
permit ESTABLISHED firewall as default cpe behaviour, and let the clients 
request policy changes from the gateway if they want other behaviour.

We have a social contract with users to have the CPE act the same way it 
did with NAT, because that's all users know. So for initial deployment the 
firewall in the CPE should act the same way the state machine in NAT does, 
but of course have UPNPv6 support so as programs get this, they will be 
able to interact with the FW.

I realise this will limit deployment of true e2e applications, but I 
believe this is unfortunately needed.

Mikael Abrahamsson    email: swmike at

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