Comment by throw0101d | Hacker News Reader

Comment by throw0101d | Hacker News Reader

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> Who was stopping anyone from doing it then, and who is stopping anyone from doing it now?

The folks who either (a) got in early on the IPv4 address land rush (especially the Western developed countries), or (b) with buckets of money who buy addresses.

If you're India, there probably weren't enough IPv4 address in the first place to handle your population, so you're doing IPv6:

* https://www.google.com/intl/en/ipv6/statistics.html#tab=per-...

Or even if you're in the West, if you're poor (a community Native American ISP):

> We learned a very expensive lesson. 71% of the IPv4 traffic we were supporting was from ROKU devices. 9% coming from DishNetwork & DirectTV satellite tuners, 11% from HomeSecurity cameras and systems, and remaining 9% we replaced extremely outdated Point of Sale(POS) equipment. So we cut ROKU some slack three years ago by spending a little over $300k just to support their devices.

* https://community.roku.com/t5/Features-settings-updates/It-s...

* Discussion: https://news.ycombinator.com/item?id=35047624

IPv4 'wasn't a problem' because the megacorps who generally run things where I'm guessing you're from (the West) were able to solve it in other means… until they can't. T-Mobile US has 120M and a few years ago it turns out that money couldn't solve IPv4-only anymore so they went to IPv6:

* https://www.youtube.com/watch?v=QGbxCKAqNUE

IPv6 is not taking off because IPv4 (and NAT/STUN/TURN) is 'better', but rather because (a) inertial, and (b) it 'works' (with enough kludges thrown at it).

There is another reason: the addresses are long and impossible to remember and hard to type.

I always bring this up and it’s always dismissed because tech people continue to dismiss usability concerns.

Even “small” usability differences can have a huge effect on adoption.

Yes, like Ethernet addresses. Those are impossible to remember, too, so obviously Ethernet is no good. /s

The solution for IPv6 addresses is the same for Ethernet addresses; don’t use them directly. Leave it to the name resolution system, and use host names.

> There is another reason: the addresses are long and impossible to remember and hard to type.

If only there was some mechanism in which we could use a human-friendly label and have that translated to a computer-usable address…

> I always bring this up and it’s always dismissed because tech people continue to dismiss usability concerns.

I don't bother remembering IPv4 addresses, so I'm not sure why I would bother to remember IPv6 addresses. Heck, phone numbers are generally short as well, and who remembers them nowadays? ("0118 999 881 999 119 725… 3")

Maybe it's dismissed because people see it as a non-issue. I regularly work at OSI Layer 2 (and even 1, pulling fibres in a DC), and Layer 3, and am not sure what the concerns are about.

The problem is that DNS is not zero configuration. ARP and NDP are which is why nobody complains about Ethernet being hard to type. DNS has to be “stood up” which is a whole extra deployment.

In modern devops in particular it is common to create and tear down IP networks in seconds and sling stuff everywhere. The extra moving part is an extra thing to break.

DNS also runs over IP which means if IP is down DNS doesn’t work. What do you have to do then? You have to debug IP without DNS.

There is mDNS but it’s not reliable and doesn’t scale to large networks. It also runs on the IP layer so if there is a problem there it can break.

> The problem is that DNS is not zero configuration.

Certainly it is not-zeroconf, but it is the same not-zeroconf for both IPv4 and IPv6.

But extra work with DHCP is needed for IPv4, and extra-extra work if you need to do things like configure 'IP helper', whereas IPv6 can be configured using only a router (which you need regardless) and some on-link packets (RAs).

> DNS also runs over IP which means if IP is down DNS doesn’t work. What do you have to do then? You have to debug IP without DNS.

And? At least you have fe80/64 as a basic starting point. Run a tcpdump to see if you're on-link in any way (or in the correct VLAN), and if you are, you can then ping(6) ff02::2 to find if there any on-link routers. You've now debugged Layer 2 and Layer 3 connectivity. Tada.

You're making IPv6 (sound) way more complicated than it is. It is no more or less complicated than IPv4 or IPX/SPX or …. It's protocol data units at OSI Layer 2 or 3 in different formats with different fields.

> who remembers them nowadays? 0118 999 881 999 119 725… 3

Me, that’s the new number for the emergency services.

Actually, that’s the only phone number I can remember :D

  Eight six seven five three oh nine
  Eight six seven five three oh nine

Also, NAT is desirable for security/network isolation reasons, and having no distinction between a local IP and a public IP has a lot of disadvantages.

Yes, there are ways to configure IPv6 to isolate subnets, separate local traffic from internet traffic, set up firewalls and DMZs, run local DNS, etc., but they're all more complicated to configure and administer than their IPv4 equivalents.

> Also, NAT is desirable for security/network isolation reasons […]

This is security theatre. People have been saying that NAT is not a security feature for over a decade:

* https://blog.ipspace.net/2011/12/is-nat-security-feature/

but the message still has not sunk in. The "Zero Trust" paper was published by John Kindervag in 2010:

* https://media.paloaltonetworks.com/documents/Forrester-No-Mo...

Most modern attacks start from a compromised internal host (e.g., from phishing), or through stolen credentials via a remote access method. The above is "castle-and-moat" thinking that tends to have weaker internal controls because it is thought the internal network is "hidden" from the dangerous outside network.

Set your firewall to default deny, then add a rule for allow outgoing connections, followed by only allow incoming connections if they are replies. For most machines (and networks), most of the time, this is what's needed: the above is applicable for both IPv6 and IPv4 (with or without NAT).

The protection comes from filtering (generally) and stateful packet inspection, not from hiding addresses.

> […] and having no distinction between a local IP and a public IP has a lot of disadvantages.

Just because something has a global addresses does not mean global reachability (see default deny above). Further you can layout your IPv6 address plan so that you can tell at a glance if hosts are externally accessible. Using a /48 a basis, you break out sixteen /52s, numbered $PREFIX:[0-f]000::/52.

To make it easier to remember what is externally accessible, you put all of those hosts in $PREFIX:e000::/52, where e stands for external. That /52 can then be broken down into:

* sixteen /56s

* 256 /60s

* 4096 /64s

or any combination thereof. See Figure A-5 for various ways to slice and dice:

* https://www.oreilly.com/library/view/ipv6-address-planning/9...

Everything in $PREFIX:[0-d,f]000::/52 is not externally reachable.

>https://blog.ipspace.net/2011/12/is-nat-security-feature/ >>Basic NAT (as defined in RFC 2663) performs just the IP address translation (one inside host to one IP address in the NAT pool). The moment the inside host starts a session through the NAT, it becomes fully exposed to the outside world.

This is a lie. A "session through the NAT" does not really expose the host to the outside world, because in 99% of the cases this is a TCP session, and the NAT machine would drop all "out of order" packets.

>Most modern attacks start from a compromised internal host (e.g., from phishing), or through stolen credentials via a remote access method.

Your statement is a perfect example of https://en.wikipedia.org/wiki/Survivorship_bias.

Most modern attacks start from an internal host exactly because NAT makes external attacks infeasible for the majority of scenarios.

>Set your firewall to default deny, then add a rule for allow outgoing connections, followed by only allow incoming connections if they are replies.

What about I don't do it, and the system is still _automatically_ secure, because NAT does exactly that while being _required_ for the system to work.

>See Figure A-5

LOL. What about I don't see any figures, and the system still works and is secure for the 99% of the cases.

> This is a lie. A "session through the NAT" does not really expose the host to the outside world, because in 99% of the cases this is a TCP session, and the NAT machine would drop all "out of order" packets.

No, it's not. NAT only translates addresses and does not inspect the TCP "internals" (like sequence number etc, which would allow it to block certain packets).

What you are describing is a stateful firewall that allows "reply packets" for an established TCP-session.

>No, it's not. NAT only translates addresses and does not inspect the TCP "internals" (like sequence number etc, which would allow it to block certain packets).

Yes it is. How would it forward response packets back if it doesn't track connections?

In real life I haven't seen "stateless NAT" for about 20 years.

But cgnat machines usually go beyond that and even verify sequence numbers.

> Most modern attacks start from an internal host exactly because NAT makes external attacks infeasible for the majority of scenarios.

Or, you know, because firewalls block stuff.

I've had hosts with public IPv4 addresses attacked on (e.g.) tcp/80 and tcp/443 because that's what the firewall allowed through so the web service was available to the public. I've had hosts with internal IPv4 addresses attacked on web ports because they were behind a (reverse proxy) load balancer for serving traffic: the fact that they had a 10/8 and were behind a NAT did not protect them from attack.

Before recently switching ISPs, my last one had IPv6 (new one does not). They activated IPv6 at some point, and I enabled it on my Asus, and suddenly all my internal devices got an IPv6 address (via RA), including things like my printer.

I had SSH enabled on my macOS laptop and desktop, but could not SSH into them from an outside source. My printer has a web interface on port 80 that I could connect to internally, but not externally. Even though all the devices had IPv6 addresses.

Just because a device is globally addressable does not mean it is globally reachable.

> What about I don't do it, and the system is still _automatically_ secure, because NAT does exactly that while being _required_ for the system to work.

Because NAT is doing that I describe, so you are doing it. The firewall is checking state on incoming packets and rejecting those that are not in its state table. The firewall is also coïncidentally just happening to also be fiddling some bits in the address field.

It is the stateful inspection that is protecting you.

* https://en.wikipedia.org/wiki/Stateful_firewall

You have a mix of accurate mix with not so much here.

> I've had hosts with internal IPv4 addresses attacked on web ports because they were behind a (reverse proxy) load balancer for serving traffic: the fact that they had a 10/8 and were behind a NAT did not protect them from attack.

You explicitly set up a NAT bypass (reverse proxy) and then claim NAT didn't protect them. If I am an external attacker coming in towards a single public IP where the backside hasn't set up UPNP/Port Forwarding/STUN/Reverse Proxy, NAT does exactly what the previous poster said. It drops packets because the 'destination' is the router itself in the packet. It has no where else to go, it has literally reached its destination.

A stateful firewall is in no way necessary for this functionality to exist. Even UDP stateless packets cannot bypass the NAT because there if there is no table tracking the conversation from the POV of the inside->out initiating the conversation because the router would have zero idea which interior host to forward the packet to and no reason to do so.

> NAT is desirable for security/network isolation reasons

For the love of expletive this mistaken belief needs to have died yesterday. NAT boxes help primarily because they also contain a firewall. But most of 2024's network security problems originate from the devices behind your firewall getting exploited through their on requests, not some random shit connecting from the outside. (Yes, that does still happen, so you keep your firewall.)

> no distinction between a local IP and a public IP

https://en.wikipedia.org/wiki/Unique_local_address

Amen! In the 2000s I had a newly setup windows xp with the modem on the internet. After 30 minutes it was toast.

Riddled with viruses.

I had the same, except I was not running it as admin, so nothing could touch system32 or the boot sector.

>But most of 2024's network security problems originate from the devices behind your firewall getting exploited through their on requests, not some random shit connecting from the outside.

That is Survivor Bias at its best.

The originate _inside_ because NAT effectively blocks all _external_ requests.

> The originate _inside_ because NAT effectively blocks all _external_ requests.

You mean the firewall effectively blocks all external requests.

Regardless, it's a fair point. Most of the attack surface on client / end user boxes these days is through social engineering and end user stupidity. Vanishingly little of it on modern OSes comes from external sources like a scan revealing a mistakenly open port. It's just that the threat profile has shifted toward making users make mistakes to the point where so much resource is thrown at fooling users now that, by the numbers and the ransomware profits, it's more effective than trying to penetrate software remotely.

That is because most systems comes with a firewall on and fairly limited surface area in the form of exposed services.

But, there are billions of other devices (IoT etc). that barely has any security protections in place that rely completely on not being exposed to the outside world.

> But, there are billions of other devices (IoT etc). that barely has any security protections in place that rely completely on not being exposed to the outside world.

Yes. And you can not-expose them via default deny firewall rule.

My home printer had an IPv6 in a prefix assigned from my ISP, but it was not accessible to the Internet (it was actually ping6-able because my Asus allowed ICMPv6 by default, but I could not connect to its web interface, like I can internally). Neither could I SSH into my macOS desktop or laptop from the outside (but could between the two internally).

And even if my globally addressable devices were globally reachable (which they were not), good luck scanning a /64.

I know. But this old NAT vs. firewall crap was pointless decades ago.

Still is.

You are technically correct that iptables is what provides the NAT functionality on Linux (by way of the MASQUERADE target), which many routers run. However, you are very incorrect that the firewall is directly involved in blocking the request.

The reason NAT works for this is because by default there are no Internet-accessible services available via the router. If a request is received by the router that doesn't match an open port, its OS will, by default, reject it, with no firewall required.

So then what’s this default firewall rule I have that blocks all non-established connections?

NAT is not required for any of the things you’re talking about.

okay now I'm curious

what happens with an incoming packet if there are no firewall rules on the NAT gateway/middlebox? without having a corresponding conntrack entry they will be dropped (and maybe even an ICMP message sent back, depending on the protocol), no?

for example if there is an incoming TCP packet with a 4-tuple (src ip, src port, dst ip, dst port) ... by necessity "dst ip" is the public IP of the NAT box, and on a pure NAT box there are no bound listening sockets. so whatever "dst port" is .. unless it gets picked up by an established NAT flow ... it will splash on the wall and getting a TCP RST.

isn't the argument that "NAT is not required", but that "NAT is implicitly a firewall"?

On a directly connected outside system, you can set a route for your LAN address space via that router and it will just work. It requires telco or physical access but I have in fact done this before.

> what happens with an incoming packet if there are no firewall rules on the NAT gateway/middlebox?

See perhaps stateless NAT:

* https://wiki.nftables.org/wiki-nftables/index.php/Performing...

>what happens with an incoming packet if there are no firewall rules on the NAT gateway/middlebox?

You get a Full Cone NAT. Once the middlebox maps an (internal IP, port) tuple to an external port, every connection to that external port would lead to that internal tuple.

Why should Host C be able to reach Host A, when Host A is only speaking to Host B?

I am sure you know this but still, I have to stress that NAT is merely a mapper from one tuple to another tuple. If your router can handle NAT it certainly can handle an IPv6 firewall. And modern home/SOHO routers come with IPv6 firewall enabled by default (for the non-home routers, you have a bigger issue if your networking guys are not checking whether firewall is active) so I find the firewall discussions utterly as meaningless as someone fearing their DHCP server is not turned on by default. And frankly speaking, it's just an excuse for not implementing IPv6 -- saying that your ISP doesn't provide IPv6 connectivity would have been more convincing.

Thanks, I wasn't familiar with this term!

I think you misunderstand my post. My "philosophical inquiry" is about trying to get to the bottom of this, and it seem to me that NAT, as virtually everywhere deployed and found in the unspeakably many SoHo setups, is a stateful NAT, and it's implicitly a bad firewall.

So when people say that this is "meme" should die .... well they are right, but not technically right, no?

> If your router can handle NAT it certainly can handle an IPv6 firewall.

The point is not that "it can", the point is that on ipv4 "it doesn't work without".

In order for ipv4 to work at all you MUST use NAT, and implicitly a firewall, those two always work together even if there the person installing the system doesn't know the word "firewall", which is usually the case.

> The point is not that "it can", the point is that on ipv4 "it doesn't work without".

Hmm. I hadn't seen this brought up and I think it's a stronger argument than most others.

The IPv6 equivalent is services on ULA only, but that's not a default behaviour.

> Yes, there are ways to configure IPv6 to isolate subnets, separate local traffic from internet traffic, set up firewalls and DMZs, run local DNS, etc., but they're all more complicated to configure and administer than their IPv4 equivalents.

Eh, I think that has hindsight bias. Setting up NAT manually, or customizing how things are NATed beyond the typical "one or two subnets/IP ranges behind a NAT gateway and maybe a DMZ" you see in businesses and residences is quite complicated! It's just that our control planes are really optimized to make that common case very easy. From router web UIs to pf presets to Windows'/NetworkManager's "share network" functionality to what articles/how-tos are available, that complexity is very effectively hidden but not removed.

As IPv6 becomes more entrenched (and more sites move to IPv6-only or public-IPv6-only deployments), the same thing that happened for the IPv4 world will happen for network segmentation configuration in the IPv6 world: it will get a lot easier and common defaults/conventions will emerge. I don't think the inherent complexity differences between IPv4 and IPv6 are that relevant here.

Modern ransomware attacks has demonstrated beyond doubt the very harmful belief that private network behind nat is an acceptable alternative to keeping systems secured and patched. The only thing nat does in a security sense is to provide false sense of security until the day a single machine inside get compromised and then the whole hospital or company comes to a standstill while rushing to restore from backup, praying that they do keep backups. Its a mistake, and the only reason it felt like a good idea was because Microsoft with windows 98/2k/xp got hit en-mass with worms targeting vulnerable windows machines that never got updates.

Thanks for pointing this out. It's hard to communicate ipv4 and I dread even reading ipv6.

I don't understand why they didn't just add two or four more fields to ipv4 e.g. 0.91.127.0.0.1 is localhost where 0.91 can be omitted in the local context.

PS: I don't understand how networking works. Feels very very complex and full of jargons.

if ipv4 is called that because there are 4 numbers in the IP address, what would you call your scheme with 6 of them?

Because the fields are there for humans, in the packet itself it’s a 32bit integer, and you can’t just arbitrarily make the src/dest fields in the packet bigger— it stops being IPv4 then.

I'm pretty sure the person you're replying to is saying that IPv6, should be IPv4 but longer, which is not at all an uncommon opinion, even if it's a breaking change to the IP protocol. And I'd argue there would've been incredibly strong benefits and much wider adoption if they did this. Sure, you'd still need new networking gear and software support to handle it, but the change is relatively simple (and potentially more easily backwards compatible), especially compared to all of the baggage that came with IPv6.

It's a fact of life that working with networking that we'll have to work with IP addresses at some level. It's easy to tell someone, "hey try typing in 'ping 8.8.8.8' and tell me what you get".

The readability of IPv6 is, in my opinion, worse with repeated symbols and more characters to remember. The symbols that were chosen were also poorly thought out. Colons are used in networking a lot of times when you want to connect to a service on a particular port, so if you want to visit 2001:4860:4860::8888 in your browser, you have to enclose the address in square brackets.

> The symbols that were chosen were also poorly thought out.

The wackiest example I've seen of this is the `ipv6-literal.net` notation for Windows UNC paths: https://devblogs.microsoft.com/oldnewthing/20100915-00/?p=12...

> I don't understand why they didn't just add two or four more fields to ipv4 e.g. 0.91.127.0.0.1 is localhost where 0.91 can be omitted in the local context.

Because they thought that 64-bits would not be enough, and did not want to have to go through yet another transition.

The IPng proposal that was chosen, SIPP, was originally 'only' 64-bits:

* https://datatracker.ietf.org/doc/html/rfc1752#section-9

See also §10.2:

* https://datatracker.ietf.org/doc/html/rfc1752#section-10.2

Specifically (§11.1):

    * scale - an address size of 128 bits easily meets the need to
      address 10**9 networks even in the face of the inherent
      inefficiency of address allocation for efficient routing

That’s because nobody normal— anyone who isn’t a tech person— remembers IP addresses.

Hell I can’t get tech people I work with to give me their public IP.

Maybe young people can’t, but older folks can easily store phone numbers in their brains, so IP4 is easy.

In practice I haven’t ever had a problem memorising IPv6 addresses. The significant proportions of any address you might type manually are 48 bits long at one end and a few bits at the other.

An example IPv4 address is 8 to 12 digits:

  10.30.115.5

A memorable IPv6 address at a /56 site — the prefix and then one or two digits — isn’t much longer:

  2001:db8:404:14::42

If you’re with a reasonably clued in ISP you probably get a /48 for your site by default:

  2001:db8:404::42

If you’re enumerating your own /64 prefixes then it’s not much more complicated than:

  site 2001:db8:404::
  net              :14::
  host                ::42

>the prefix and then one or two digits — isn’t much longer

I'd argue it's just enough to make the difference though.

The problem is that people got used to being able to rely on memorizing IP addresses. IPv6 does its best at making IP addresses both harder to memorize, and completely dynamic, going so far as to change the IP on a fairly regular basis. It's antithetical to some very core qualities that an IP address is supposed to have in the minds of many.

This is the first time I read about someone actually trying to remember IP6 addresses, maybe I should try that, because it’s really easy to remember IP4. For me, the problem is that there’s hex numbers, which are harder to remember and missing zeros, so you need remember the colons. If IP6 would just be 6 decimal numbers and this would be the default way of writing them, this would not be a problem. But it feels to me that the cryptic way IP6 is written is to make it hard for humans to remember it.

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