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IPv6 - Can We Turn the Global Network into a Firewall Protecting All End Users?

One recurring argument against implementing IPv6 in campus networks is the absence of Network Address Translation (NAT). While NAT is perceived as a security mechanism in IPv4, we need to rethink our approach when working with IPv6. Instead of relying on NAT, we can leverage firewalls to safeguard endpoints.

In IPv6, every device receives a routable address. To protect endpoints effectively, we require firewalls to filter unwanted traffic. But what if we could stop such traffic at the source? Could this approach convince more people toward adopting IPv6?

 


According to RFC 7381: “In a /48 assignment, typical for a site, there are then still 65,535 /64 blocks.” and “All user access networks should be a /64.”

 

Can we use then bit 63 to convey a message: “I don’t want any incoming traffic initiated towards me!!!”? Of course response would be accepted.

 

We could divide the /64 allocations into two groups: one for servers, and these accept incoming traffic (bit 63 = 0):

 

for example 2001:0db8:0000:0000::/64

 

And the second group: endpoints, these never accept incoming traffic (bit 63 = 1):

 

for example 2001:0db8:0000:0001::/64

 

We only need all systems to understand the message. If a router or firewall sees such packet, then drops it. From the obvious reasons it can be applied only for TCP. 

 

Every TCP packet with flag SYN, where destination address (IPv6) has bit 63 equal 1, must be dropped.

 

I know it increases the consumptions but let me just remind what we have available:

 

 

Number of IPv6 addresses:         340.282.366.920.938.000.000.000.000.000.000.000.000 

Number of people (Jan 2024):                                                                        8.019.876.189

Number of IPv6 for each person:                        42.429.877.831.239.700.000.000.000.000

Number of IPv4 addresses:                                                                            4.294.967.296

 

Is it realistic or am I dreamer? Can you challenge this idea?


RFC 7381https://datatracker.ietf.org/doc/html/rfc7381

NAT IPv6 https://en.wikipedia.org/wiki/IPv6-to-IPv6_Network_Prefix_Translation

NAT IPv6 https://blogs.infoblox.com/ipv6-coe/you-thought-there-was-no-nat-for-ipv6-but-nat-still-exists/

 

 

Edit (25 Apr 2024):

 

After discussion with some experts there is a problem with checking the SYN flag in the TCP flow. We don't inspect everything and it could be too much demanding. Quick assessment of bit yes, but not SYN flag in TCP.

 

 

 

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