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DHCPv6-PD – First Steps

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Re: DHCPv6-PD – First Steps

#31

Post by hairyplanter »

zamadatix wrote: post #26
ninkendo wrote: post #23

This article hints at what I consider to be the biggest technical drawback to IPv6 for residential use, which is that dynamic prefixes mean your internal LAN IPs are never stable. The answer to this is usually something like “duh, use DNS”, but how are you going to configure that DNS server if your whole network’s IP address range could change at any time? Yes, multicast DNS is a thing, but it’s not supported in all…

For those with flatter home network needs but still wanting a few things internal to be reachable by IP I'll throw in you can also use static link locals on fe80:: instead of a random ULA prefix. You'll still need the ULA method if you have multiple subnets and want static services reachable via routing though. Unless the router says the old prefix now has a valid lifetime of 0 the proper thing to do is actually to w…

As browsers don't like link local addresses in the address bar, ULA is still better.

Re: DHCPv6-PD – First Steps

#32

Post by hairyplanter »

zamadatix wrote: post #28
justahuman74 wrote: post #25

Earlier quoted context omitted.

I wish getting and using an IPv6 subnet was like buying a domain name, and that residential ISPs would be required to use your subnet for your service, a bit like portable phone numbers. The current IP allocation/usage procedures are a bit beyond most people

A good compromise between this (lots of routing work on the internet) and random prefixes all the time (lots of work on the end user networks) is setting DHCP-PD to do consistent PD assignments. Sure, you're space isn't portable between carriers if you move/have redundant internet but you can also rely on a static address in your assigned range working 3 years from now even if your router is offline for a month. ATT…

ULA is still the right solution here.

ULA would let you maintain your internal lan with custom subnets and DNS even if you switch carriers or use multiple carriers. No need to update your internal DNS servers for ULA.

If you're running a server on your dynamic residential service, you must be using dyndns for ipv4. So do the same with ipv6.

Residential random prefixes is the nature of residential networks, as ISPs don't want to preserve state. With a business grade service, you'd get a static prefix, much like static ipv4. Then the only time you need to update anything is when you switch your ISP and need to update global DNS addresses for your servers.

Re: DHCPv6-PD – First Steps

#33

Post by Uptrenda »

People who advocate for IPv6 are always like 'ahhhh just plug it in and its ready to go!!!' There's even twitter accounts that shame people for how they approach IPv6. But after doing a crap load of network programming I can tell you its really not simple at all.

- IPv6 has many different address types.

- Depending on the type you want to bind to it needs to be handled different.

- Some types need an interface ID appended to them.

- This is conditional on the type of the OS.

- Windows has no easy way to get the ID programmatically.

- Some address types need additional bind info like the 'scope id.'

- Whether you can reach a specific addr type in a con depend on the addr you bind to.

- IPv6 was designed to have plenty of addresses so that NAT isn't needed. Guess what: IPv6 can still do NAT like NAT6. In which case you won't have any nice global scope addresses to bind to.

Writing good network code depends on being able to list the interfaces on a machine and the addresses that they have. With IPv6 this is desirable since it lets you know if you have any global scope addresses, what your local-scope addresses are, and other kinds. But from what I've seen seen most programming languages fall back to using default routes for everything. This means that the programmer literally can't lookup the addresses and interfaces for their software.

Also lastly: getting a modern router that properly supports IPv6 isn't easy at all. I literally have a cupboard filled with PoS routers that can't do IPv6 properly. Everything that Telstra and Optus tend to give customers; most Dovado routers; GL inet routers (can do NAT6 but who wants that); 'netgear nighthawk' (I found a security vuln in netgears router when testing v6); and so on. People will say 'just slap Open-wrt on something and call it a day.' But these are the kinds of people who will spend 120+ hours reading the open-wrt wiki and learning electronic basics to setup a custom router. What they think is 'easy' doesn't take into account all the time they've already spent learning such niche BS. I have better things to do than (((just waste 1 billion hours with open-wrt and end up with someone that still doesn't work.)))

'IPv6 is easy. It just works.'

Re: DHCPv6-PD – First Steps

#35

Post by lloeki »

hairyplanter wrote: post #30
ninkendo wrote: post #23

This article hints at what I consider to be the biggest technical drawback to IPv6 for residential use, which is that dynamic prefixes mean your internal LAN IPs are never stable. The answer to this is usually something like “duh, use DNS”, but how are you going to configure that DNS server if your whole network’s IP address range could change at any time? Yes, multicast DNS is a thing, but it’s not supported in all…

> or just bite the bullet and use ULA. This is the proper ipv6 solution. With ipv6, one ethernet interface is _supposed_ to have multiple addresses. You wouldn't want your lan routing to stop working when your ISP goes down, right? So configure your internal DNS with ULA (which should be stable for each machine for a given prefix, even with SLAAC) and be done with it, much like internal DNS using private addresses in…

> the ISPs want a stateless solution, so customers get a dynamic prefix. Maintaining the same prefix across power outages needs a stateful solution, so only business plans offer them for an extra fee, much like static ipv4 addresses.

I'm surprised based on my experience: in 15 years of residential IPv6 usage I've always had the same IPv6 prefix (for a given ISP contract of course), even for those ISPs that insisted on handing out dynamic IPv4 with no option for a static one plus had no qualms renewing the IP at any moment, not just power down.

> stateful solution

I'm seeing this the other way around: dynamic needs lease tracking while static just needs a permanent record attached to the already present auth mechanism.

Re: DHCPv6-PD – First Steps

#36

Post by hairyplanter »

lloeki wrote: post #35
hairyplanter wrote: post #30

Earlier quoted context omitted.

> or just bite the bullet and use ULA. This is the proper ipv6 solution. With ipv6, one ethernet interface is _supposed_ to have multiple addresses. You wouldn't want your lan routing to stop working when your ISP goes down, right? So configure your internal DNS with ULA (which should be stable for each machine for a given prefix, even with SLAAC) and be done with it, much like internal DNS using private addresses in…

> the ISPs want a stateless solution, so customers get a dynamic prefix. Maintaining the same prefix across power outages needs a stateful solution, so only business plans offer them for an extra fee, much like static ipv4 addresses. I'm surprised based on my experience: in 15 years of residential IPv6 usage I've always had the same IPv6 prefix (for a given ISP contract of course), even for those ISPs that insisted o…

My experience is the opposite!

Re: DHCPv6-PD – First Steps

#37

Post by yjftsjthsd-h »

hairyplanter wrote: post #32
zamadatix wrote: post #28

Earlier quoted context omitted.

A good compromise between this (lots of routing work on the internet) and random prefixes all the time (lots of work on the end user networks) is setting DHCP-PD to do consistent PD assignments. Sure, you're space isn't portable between carriers if you move/have redundant internet but you can also rely on a static address in your assigned range working 3 years from now even if your router is offline for a month. ATT…

ULA is still the right solution here. ULA would let you maintain your internal lan with custom subnets and DNS even if you switch carriers or use multiple carriers. No need to update your internal DNS servers for ULA. If you're running a server on your dynamic residential service, you must be using dyndns for ipv4. So do the same with ipv6. Residential random prefixes is the nature of residential networks, as ISPs do…

I guess I'll ask here... How do I learn this? I'm comfortable with IPv4, including DHCP, DNS, VPNs, NAT, whatever. I'd like to be able to set up a v6 network[0] in whatever is the Correct and sane way. Is there a good end-to-end tutorial to set it all up by hand and explain what all these things (RA/DHCPv6/fe80::/ULA/etc.) are and how to use them or why not to use them?

[0] Ideally pure v6 if possible; I think there's some way to encapsulate/NAT v4 traffic out from a pure v6 network so I don't actually need dual stack.

Re: DHCPv6-PD – First Steps

#39

Post by Tigress8780 »

mathsmath wrote: post #18
Dylan16807 wrote: post #17

Earlier quoted context omitted.

Who's out there being so crazily stingy? Allocating a subnet that small is making things more complicated for no benefit.

Someone should double check me, but I think PD less than a /64 also just breaks (and probably is against the spec). A lot of the complaints I have seen in the last decade is from ISPs doing silly things and cutting their teeth on fresh IPv6 deployments. My ISP seems to have their collective ducks in a row now, and it has been rock solid for years. I actually had a case recently where a misbehaving IPv4 IoT device con…

It probably is. I remember that putting a /72 into OpenWRT's `ip6prefix` field actually breaks the whole network stack (including IPv4, the interface no longer has any address assigned to it).

Re: DHCPv6-PD – First Steps

#40

Post by jeroenhd »

ninkendo wrote: post #23

This article hints at what I consider to be the biggest technical drawback to IPv6 for residential use, which is that dynamic prefixes mean your internal LAN IPs are never stable. The answer to this is usually something like “duh, use DNS”, but how are you going to configure that DNS server if your whole network’s IP address range could change at any time? Yes, multicast DNS is a thing, but it’s not supported in all…

My IPv6 address is perfectly stable. It's up to the ISP to decide if they bully you into paying extra for a static network or not, but it's an implementation problem. Same with IPv4 assignment, necessitating hacks like DynDNS.

If you want stable local addressing, announce a ULA on your LAN. Not all routers support it, unfortunately, but you can announce a ULA from any device. Just don't announce your raspberry Pi as an outbound router.

ULAs use SLAAC and will derive at least one IP address from your devices' MAC address. There's a chance of instability if you have devices with the same MAC addresses (there's detection for that problem but you end up with a race condition after a network reboot), but your network will probably break in other ways if you have such a setup.

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