nanog mailing list archives

Re: Assigning IPv6 /48's to CPE's?


From: Valdis.Kletnieks () vt edu
Date: Thu, 03 Jan 2008 23:57:49 -0500

On Thu, 03 Jan 2008 10:17:37 EST, William Herrin said:

In my ever so humble opinion, IPv6 will not reach significant
penetration at the customer level until NAT has been thoroughly
implemented. Corporate information security officers will insist.
Here's the thing: a stateful non-NAT firewall is automatically less
secure than a stateful translating firewall. Why? Because a mistake
configuring a NAT firewall breaks the network causing everything to
stop working while a mistake with a firewall that does no translation
causes data to flow unfiltered. Humans being humans, mistakes will be
made. The first failure mode is highly preferable.

Which is why, if your site has an *actual* clue, the deployed hosts *also*
have their own iptables/ipfilters/whatever-windows-calls-it rulesets that
say what hosts are allowed to talk to them. So on the server, I can do:

ip6tables -A tcp-in -s ! 2001:468:c80/48 -p tcp --dport 22 -j DROP

Now, even if our firewall guys fumble-finger something, I won't get
SSH connections coming in from outside AS1312.

Of course, I can't talk about business pressures from customers that have
incompetent security officers that don't understand stuff like multiple
layers of defense...

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