Setup NAT64 in pfSense

imcdona

Since pfSense hasn't yet added support for NAT64 I was looking into how difficult it would be to manually add the required rules. Here is the original commit to FreeBSD adding support for NAT64. The comment on the commit provides the following instructions:

Stateless NAT64 registers external action with name nat64stl. This
keyword should be used to create NAT64 instance and to address this
instance in rules. Stateless NAT64 uses two lookup tables with mapped
IPv4->IPv6 and IPv6->IPv4 addresses to perform translation.

A configuration of instance should looks like this:
 1. Create lookup tables:
 # ipfw table T46 create type addr valtype ipv6
 # ipfw table T64 create type addr valtype ipv4
 2. Fill T46 and T64 tables.
 3. Add rule to allow neighbor solicitation and advertisement:
 # ipfw add allow icmp6 from any to any icmp6types 135,136
 4. Create NAT64 instance:
 # ipfw nat64stl NAT create table4 T46 table6 T64
 5. Add rules that matches the traffic:
 # ipfw add nat64stl NAT ip from any to table(T46)
 # ipfw add nat64stl NAT ip from table(T64) to 64:ff9b::/96
 6. Configure DNS64 for IPv6 clients and add route to 64:ff9b::/96
    via NAT64 host.

Stateful NAT64 registers external action with name nat64lsn. The only
one option required to create nat64lsn instance - prefix4. It defines
the pool of IPv4 addresses used for translation.

A configuration of instance should looks like this:
 1. Add rule to allow neighbor solicitation and advertisement:
 # ipfw add allow icmp6 from any to any icmp6types 135,136
 2. Create NAT64 instance:
 # ipfw nat64lsn NAT create prefix4 A.B.C.D/28
 3. Add rules that matches the traffic:
 # ipfw add nat64lsn NAT ip from any to A.B.C.D/28
 # ipfw add nat64lsn NAT ip6 from any to 64:ff9b::/96
 4. Configure DNS64 for IPv6 clients and add route to 64:ff9b::/96
    via NAT64 host.

I'm new to FreeBSD but from what I understand there's three firewall applications available, IPFW, PF and IPF. The example provided is based on IPFW. How would I go about implementing the IPFW statements above in PF, specifically pfSense? Is this doable?

In regards to DNS64, adding this line to the custom options in the Unbound module enables DNS64 support:

module-config: "dns64 validator iterator"

Alternatively you can use Google's public DNS64 servers.

Am I being naive or can I enable NAT64 in pfSense on an experimental basis with a few custom pf rules?

JKnott

Why would even want to use NAT on IPv6?? NAT is a hack to get around the IPv4 address shortage. No such shortage exists on IPv6.

imcdona

@jknott said in Setup NAT64 in pfSense:

Why would even want to use NAT on IPv6?? NAT is a hack to get around the IPv4 address shortage. No such shortage exists on IPv6.

NAT64 isn't "natting" in the traditional sense. NAT64 allows IPv6 only hosts to reach IPv4 hosts. Large companies such as Microsoft are using NAT64 and going IPv6 only because they've run out of RFC 1918 addresses.

Here's an article describing Microsoft's move to NAT64

JKnott

Sorry, I hadn't had my morning beer yet, when I posted that. ;)

Actually, a better solution is 464XLAT, which avoids some of the problems with NAT64. Some carriers are now using that.

johnpoz

Sounds like bad planning on MS if they are running out of rfc1918 space... As of last count I see their employee number at 124K.. Well the 10/8 allows for 16.7 Million IPs - that a shit ton of IPs per person ;)

That is not counting the rest which is nothing to sneeze at either 172.16/12 over a million..

So while MS for sure is large - making comments that they have exhausted rfc1918 is BS if you ask me.. I am sure a re IP of their sites could free huge amounts of space..

JKnott

@johnpoz said in Setup NAT64 in pfSense:

Sounds like bad planning on MS if they are running out of rfc1918 space

Comcast had the same problem. There weren't enough RFC1918 addresses available for them to seamlessly manage their network.

imcdona

@johnpoz said in Setup NAT64 in pfSense:

So while MS for sure is large - making comments that they have exhausted rfc1918 is BS

Don't take my word for it. From the article I linked to above:

The depletion of public IPv4 space is well-known, but Microsoft IT has exhausted almost all RFC1918 space.

@jknott said in Setup NAT64 in pfSense:

Actually, a better solution is 464XLAT, which avoids some of the problems with NAT64.

I'm no expert in IPv6 transition technologies so please correct me if I'm wrong, but from what I understand, NAT64 is still required when using 464XLAT. The issue that 464XLAT solves is IPv4 literals (trying to access a host by IP address instead of a DNS hostname). If an IPv6 only client attempts to connect to 1.2.3.4 directly there's no opportunity for DNS64 to translate the address. In those circumstances, a CLAT daemon is used on the CLIENT device to translate that address to an IPv6 address. But yeah, ideally clients should have CLAT enabled if you want a proper setup.

JKnott

With 464XLAT, you run dual stack, so that IPv4 addresses can be used to access IPv4 servers. In the process, IPv4 is converted to IPv6 and back again. It all happens transparently.

johnpoz

@imcdona

I read the article and saw that - and what I am saying is BS.. Sure you can use up anything with bad management.. Sorry but they are not big enough to use it up if they would of planned correctly.

They do not have enough employees to justify all 17 plus million IPs being gone with proper planning.

JeGr

@johnpoz said in Setup NAT64 in pfSense:

I read the article and saw that - and what I am saying is BS.. Sure you can use up anything with bad management.. Sorry but they are not big enough to use it up if they would of planned correctly.

As there are currently MS speakers in Heidelberg talking about IPv6 in internal use and having heard and read their presentation, there's no BS involved or "bad management" at all. One just has to take into account that with MS there is also:

Linkedin
Nokia
GitHub
Azure Cloud

and various other aquisitions and connections to multiple destinations, datacenters etc. round the globe. Nothing to do with "just clients" or emplyoees. As one can see from the presentation of their CSEO here:

https://twitter.com/Enno_Insinuator/status/1107919913707061248

they are calculating that at max they have 2-3y left until they can't move with RFC1918 anymore. So they are - and more should go that route - actively working on IPv6, IPv6 only abilities, security etc. Just to clear up that "confusion" - it doesn't have to be a company or management etc. "at fault" for RFC1918 address space to become exhausted. :)

johnpoz

Sorry again BS... Nokia doesn't need to talk to github, or linkedn directly... All of those places can use the same rfc1918 space.. So each one of those have the full rfc1918 space to work with.

The whole point of rfc1918 is it can be used at each location, etc. etc.

JeGr

What has to talk to each other and how and why - you know that? I don't. So if your magic eight ball has more insight than mine, I'm jealous ;) But I take the word from their network and security staff talking about their problems seriously and don't simply dismiss it as bullshit without further insight. :)
Also working for a big US tech company with "C" I've seen a LOT of private adressranges needed and used in software testing and development alone. So I'm sure that at MS you'll see even more of them in use. And yes, they often have to talk to each other. Sadly :/

johnpoz

They are running out of IPv4 rfc1918 space because they choose to do so.. Plain and simple!

Sure some devices might need to talk to each other.. Not ALL of them!! And if need be they can nat, etc. etc.. Sorry but they are touting their move to ipv6 like they are doing something innovative.. And they are using it as marketing.. they don't NEED to move to it..

Which is GREAT... But don't tell me you "have to" because your out of rfc1918 space.

And to be honest here is the big problem with the eventual migration... Is once you move part of the network to IPv6.. That frees up lots of IPv4 that can be used now..

For example could their management vlans on Ipv6, they could put their storage vlans on IPv6, they could put xyz on IPv6, etc etc.. This frees up LOTS of address space to use where its needed, etc.

bimmerdriver

The point of IPv6 is not to free up IPv4 address space so people can keep on using IPv4, it's to completely replace IPv4.

Whether you like Microsoft or not, they have built more hosts that support dual-stack networking than any other company, probably by a significant margin if you count the number of licenses of all windows and windows server versions that support IPv6. As @JKnott pointed out, this began with Windows XP SP3, which was launched on April 21, 2008. That's a lot of hosts.

So I think Microsoft has people capable of reorganizing an IPv4 network, if they thought it was the approach to take. I'll give them the benefit of the doubt that if it if was more practical / expedient / cost effective / ..., they would have reorganized their IPv4 address space. Apparently, they decided to go with IPv6. Again, so much for claims that no one is using IPv6...

JKnott

@johnpoz said in Setup NAT64 in pfSense:

They are running out of IPv4 rfc1918 space because they choose to do so.. Plain and simple!

I read an article, a while ago, about how Comcast couldn't manage their network with IPv4, without breaking it into segments, due to a lack of RFC 1918 addresses.

imcdona

@JKnott said in Setup NAT64 in pfSense:

I read an article, a while ago, about how Comcast couldn't manage their network with IPv4, without breaking it into segments, due to a lack of RFC 1918 addresses.

Yup. Comcast ran out of RFC1918 addresses back in 2005. Here's an interesting presentation that Comcast gave regarding the challenges of managing a 100+ million IP addresses and their IPv6 migration strategy.

According to the presentation they use 8-9 IP addresses per household. Things got so tight they actually started using public space for device management.

chrcoluk

I think a common mistake made is to assume NAT only has one purpose "to address ip space shortage", when that assumption is made, then another assumption gets made which it has no purpose on ipv6. Then there is the third assumption which is that every isp allocates a static routeable ip block.

In the real world however these scenarios exist.

Some isp's do give out /128's.
People may prefer to use consistent internal addresses even on IPv6 and not have routeable IPv6 on every device. This will be especially the case if the isp provides dynamic prefixes.
Outbound NAT is used to divert outbound traffic e.g. to force all outbound DNS to go via one resolver.

The argument might be made that if an isp gives out a /128, a solution shouldnt be present for that situation and instead the user should ditch the isp, I dont agree with that mentality, plus the other two situations I detailed are clear legitimate uses of NAT. Although one could say NPt might satisfy the second scenario which then just leaves the outbound NAT situation, for the 3rd scenario I cannot think of anything else that could be done as a substitute, other than using a VPN which I consider way more complex and intervening than NAT.

My opinion of this subject is that NAT64 and NAT66 should be a feature on every router type device, but at the same time discouraged, so off by default, and not as accessible as IPv4 NAT. But I think the approach of refusing to accept these as features of IPv6 and as such keeping them off devices is not the right way to go.

One thing proving this point is there is an article on the internet, from a guy who absolutely hates NAT, the article itself is a guide on how to setup NAT66, basically his provider only provided a /128, he assessed his options, which were to use a he.net tunnel, to change provider (he didnt mention this one, but is assumed he loved the price and features of provider too much to consider it), or to setup NAT66. He admitted going the he tunnel route was messier, and worse latency than a simple NAT configuration so went the NAT66 route.

Thanks to the OP tho as this guide might be a way to "properly " sort out my ipv6 dns leak problem, I find my current solution of simply having a reject firewall rule as "hacky" as the requests will be made and denied before a successful request is made. Whilst outbound NAT makes the software making the request think its had a successful lookup from its chosen dns server. So works transparently.

The issue is tho, is of course how does one get the NAT64 rules to auto apply on every PF reload, and sadly I dont know the solution as I dont think there is a hooking mechanism provided to trigger script execution on firewall reload.

--

Think this is a no go without pfSense official support, it requires IPFIREWALL_NAT64 compiled in the kernel, and its not in GENERIC.

JKnott

@chrcoluk said in Setup NAT64 in pfSense:

Some isp's do give out /128's.

The /128 is generally used to identify a system and since it's a /128 it's not possible to communicate with it directly. Traffic must be routed to it. Are there any ISPs that hand out a single IPv6 address? Even my cell phone gets a /64. The only time I've seen a /127 assigned was with the 6in4 tunnel provider I used to use. Depending on configuration, either a /127 single address or a /56 prefix were available. I used the /56 on my home network and the /127 on my notebook computer, when away from home.

People may prefer to use consistent internal addresses even on IPv6 and not have routeable IPv6 on every device. This will be especially the case if the isp provides dynamic prefixes.

You'd use Unique Local Addresses for that. ULA are the IPv6 equivalent to the IPv4 RFC 1918 addresses.

which then just leaves the outbound NAT situation, for the 3rd scenario

Why would you need outbound NAT, when you have so many addresses available. NAT was sometimes used when combining networks that have overlapping addresses. But that's a problem that arose through using NAT. It could never happen when using public addresses.

I have yet to see a use for NAT that wasn't caused by the IPv4 address shortage.

NAT is used to get around the IPv4 address shortage. There is no need for it on IPv6, other than someone being incompetent.

dotdash

@JKnott said in Setup NAT64 in pfSense:

I have yet to see a use for NAT that wasn't caused by the IPv4 address shortage.

NAT is used to get around the IPv4 address shortage. There is no need for it on IPv6, other than someone being incompetent.

I have a lot of experience with v4, but little with v6. I f nat is useless please explain how I handle situations such as: A client changes ISPs- do I re-address every device? What about multi-wan? Is 'prefix' translation not the great satan that network translation is? And don't tell me to get every small business a block from IANA, because they charge as much for 6 as they used to for 4.

JKnott

@dotdash

A client changes ISPs- do I re-address every device?

Changing device addresses is very easy on IPv6, as you normally don't set them at all. The router provides the prefix and the device provides it's own suffix via SLAAC or DHCP.

What about multi-wan?

IPv6 actually supports that. You can get connections from as many ISPs as you want and assign priority, etc.. If you change prefixes, you'd have to update DNS accordingly, but that's about all.

Is 'prefix' translation not the great satan that network translation is?

The problem is NAT breaks some protocols. One of the first that broke was FTP, when used with command line clients. Some couldn't use passive mode, which was needed to work through NAT. More recently, it breaks IPSec Authentication Headers, which is one of the security mechanisms that IPSec provides. You also need STUN servers, to get around NAT, with VoIP and some games.

And don't tell me to get every small business a block from IANA, because they charge as much for 6 as they used to for 4.

Well, I managed to get a /56 from my ISP and another from a 6in4 tunnel provider I used to use. The tunnel service was free and my Internet access isn't that expensive. I have no idea what addresses sell for, but I understand IPv4 addresses are becoming more expensive. Also, if you're buying address blocks, you're also buying a much higher level of service from a carrier, rather than an ISP. I have set up many fibre connections to corporate customers. They tend to get an Ethernet connection, rather than IP, from the carrier.

Because of NAT and trying to save address space, many people have developed bad habits that wouldn't have occurred had sufficient address space been available. According to Vint Cerf, IPv4 was only intended to be a proof of concept system and he planned to go to a much larger address space in the "official" IP>