Understanding IPV6

Is there a good guide to the use of IPV6 in a domestic environment?

In reply to a post by Michael_Chare:

Is there a good guide to the use of IPV6 in a domestic environment?

As a general rule you shouldn't really have to do much. Most modern devices (laptops, tablets and phones) will support it and if your provider has given you a service that supports it, it will usually "just work". What exactly are you trying to do with it?

There is a beginners guide here if you wish to learn how it works:

https://www.youtube.com/watch?v=z7Al3P8ShM8

As Seb says, it will usually just work with supplied ISP routers.

One thing some get concerned about is the public nature of IPv6 addresses. Many of us who tinker with networks have grown used to NAT and that our devices in the home have private IP addresses, so are hidden away, but with IPv6 each device gets a public IP address and this somehow feels insecure. However all ISP routers will have firewalls that default to blocking incoming traffic, so even with a public IPv6 address our devices are protected by the firewall and all incoming traffic is blocked. Only traffic coming back in reply to an outgoing connection is allowed back to our devices.

Also because there are so many addresses, scanning for devices to find them is hard, for example, you will likely have at least 18,446,744,073,709,551,616 possible public IP addresses in your home, and devices don't start at 1, they randomise their address, so its hard for someone to just probe your network.

In reply to a post by Michael_Chare:

Is there a good guide to the use of IPV6 in a domestic environment?

Many parents turn it off at the router, as they rely on things like MAC address to device being sticky to use in firewall rules for content screening or limiting internet access at bedtime. (In theory domestic IPv6 should use the MAC in the address, but the nature of the addresses blow most non-IT people's minds).

Some very large UK ISPs still don't provide IPv6, including mine (Virgin Media), and there are currently no major US / UK internet services that only work on IPv6. However in Asia the opposite is common, without v6 many sites disappear, but these are generally not in English.

In reply to a post by seb:

In reply to a post by Michael_Chare:

Is there a good guide to the use of IPV6 in a domestic environment?

As a general rule you shouldn't really have to do much. Most modern devices (laptops, tablets and phones) will support it and if your provider has given you a service that supports it, it will usually "just work". What exactly are you trying to do with it?

I would just like to learn about IPV6 to the extent that I fully understand how a domestic IPV6 network works. Neither of the two ISPs I have connections to support IPV6 at the moment.

For example to configure one local device I have to use IPV6, I have to choose whether the IPV6 mode should be 'route advertisement', DHCP or manual. I would like to understand the implications of using these alternatives.

There are not really any implications and you can have DHCP and Router Advertisements enabled, however some devices don't support DHCP so Router Advertisements has to be a minimum really. You wouldn't normally ever manually set IPv6 addresses, but you can if you wanted a more memorable one I suppose.

DHCP for IPv4 was a way of managing a very small range of IP addresses on the internal side, perhaps a couple of hundred, and it meant devices got given unique IP addresses.

With IPv6 on your Internal network you would have 18446744073709551615 public IP addresses for any device to choose from, so we no longer need something like DHCP micro managing each IP address, and the device itself can just generate a random one, and the chances of choosing one already in use is very very small, plus devices will check first that no one has the same IP they have randomly picked. The device just needs to know the first 64 bits of the IPv6 address and that is what the router is advertising, and the device can randomly assign the other 64 bits to be a unique address.

Windows uses DHCP as well as RA on IPv6, so if DHCP is enabled for handing out IP addresses, Windows will get one DHCP address and then make up one or more random ones to use on the Internet, this is for security and privacy as it can then discard the address and pick another random one later, so websites have a harder time tracking the device.

So on peer to peer networks (e.g. 3 windows PCs on a home LAN) the idea of managing them by IP (v4) disappears. Not many home routers support DDNS registration (as we have in corporate Windows LANs) so finding a PC by name is going to be a game of broadcast again?

Many parents disable IPv6 so they can control (on a firewall type device) their teenagers access to the internet by time... made harder by mobile devices randomising the MAC address

In reply to a post by jchamier:

So on peer to peer networks (e.g. 3 windows PCs on a home LAN) the idea of managing them by IP (v4) disappears.

When a PC wakes up on my Windows network, all the other machines can connect to it by its name, which is automatically associated with a local IPv4 address in the router's DNS server.

Whether it's possible to do the same with an IPv6 address I don't know, but given no-one is switching off IPv4 anytime soon on their home networks, I assume IPv4 will be suitable for automatic LAN hostname mapping for quite some time.

I suppose I could also look into utilising the static local addresses (IPv6 ULA and link-local addresses), but I have no need.

In reply to a post by Oliver341:

When a PC wakes up on my Windows network, all the other machines can connect to it by its name, which is automatically associated with a local IPv4 address in the router's DNS server.

Do you define manually in your router DNS, or use a DDNS ? I'm used to corporate on-premises AD where DDNS is automatic. The ISP routers I am familiar with have no such thing as a DNS, at best they are proxy to the ISP DNS, and don't resolve for short names (no FQDN).

Whether it's possible to do the same with an IPv6 address I don't know, but given no-one is switching off IPv4 anytime soon on their home networks, I assume IPv4 will be suitable for automatic LAN hostname mapping for quite some time.

Yes, dual-stack is going to live for quite a while.

I suppose I could also look into utilising the static local addresses (IPv6 ULA and link-local addresses), but I have no need.

My ISP doesn't do IPv6, so its all theoretical here. (Virgin Media).

In reply to a post by jchamier:

Do you define manually in your router DNS, or use a DDNS ? I'm used to corporate on-premises AD where DDNS is automatic. The ISP routers I am familiar with have no such thing as a DNS, at best they are proxy to the ISP DNS, and don't resolve for short names (no FQDN).

When a Windows PC is connected to my Sky router, the DNS server on the Sky router automatically creates a DNS record for it.

E.g.
1) I connect PC2, e.g. called "PC2", to my Sky Router
2) The Sky router automatically creates a DNS entry for PC2 and maps it to e.g. 192.168.0.6
3) On PC1 I can then ping PC2 by doing "ping PC2"

I assume pinging PC2 would break if the DNS servers on PC1 are set to e.g. Google DNS instead of the Sky router.

In reply to a post by Oliver341:

When a Windows PC is connected to my Sky router, the DNS server on the Sky router automatically creates a DNS record for it.

Useful, not something Plusnet, or Virgin Media routers do. Thanks!

In reply to a post by Oliver341:

When a Windows PC is connected to my Sky router, the DNS server on the Sky router automatically creates a DNS record for it.

Are you sure? I have a Draytek 2762 and it doesn't do that. Windows machines find each other via NetBIOS on my network. This was actually a problem for me when I started working at home because I sometimes have to do mobile app development and neither the Android nor the iPhone I use for testing could find the server hosted on my development PC.

I had to assign a static IP address to my development PC then manually create a DNS entry for that machine on the router. My colleagues had the same problem but some of them were relying on ISP routers that didn't support that kind of configuration so they ended up having to edit the hosts file on the phones.

Edited by Andrue (Sat 11-Mar-23 22:16:21)

In reply to a post by Andrue:

Are you sure?

Yes. Here I am querying my router's DNS server directly for the hostname of one of my PC's on the network:

C:\>nslookup pc2. 192.168.0.1
Server: SkyRouter.Home
Address: 192.168.0.1

Non-authoritative answer:
Name: pc2
Address: 192.168.0.5

In reply to a post by Oliver341:

In reply to a post by Andrue:

Are you sure?

Yes. Here I am querying my router's DNS server directly for the hostname of one of my PC's on the network:

C:\>nslookup pc2. 192.168.0.1
Server: SkyRouter.Home
Address: 192.168.0.1

Non-authoritative answer:
Name: pc2
Address: 192.168.0.5

And it was automatic? That surprises me.

https://unix.stackexchange.com/questions/652096/how-...

So that post does suggest that some routers will assign the hostname via DHCP. I'm intrigued that Sky's router does though. That link seems to imply that it's an 'enterprise' router feature. That seems a bit odd with the description given in the first reply to this thread:

https://helpforum.sky.com/t5/Broadband/SR203-DNS-and...

'I do not dispute that the Sky hub is basic and a bit cr*p but it does the job it is intended to do according to your contract with Sky.'. That reply also implies that the router's DNS is locked down so maybe it was done to overcome an enforced limitation?

But hey, you live and learn

Edited by Andrue (Sun 12-Mar-23 08:48:49)

In reply to a post by Oliver341:

Yes. Here I am querying my router's DNS server directly for the hostname of one of my PC's on the network:

And on my Asus, I get:
*** No internal type for both IPv4 and IPv6 Addresses (A+AAAA) records available for <hostname>.

In reply to a post by Andrue:

And it was automatic? That surprises me.

Yes, automatic. The router also creates DNS records for smartphones connected to it:

C:\>nslookup HUAWEI_P_smart_2019-a427e. 192.168.0.1
Server: SkyRouter.Home
Address: 192.168.0.1

Non-authoritative answer:
Name: HUAWEI_P_smart_2019-fee9b
Address: 192.168.0.3

In reply to a post by Oliver341:

Yes, automatic. The router also creates DNS records for smartphones connected to it

Its quite easy to do with open source software on Linux, but it is interesting the router designers actually bothered to do it!

A Linux or Windows DHCP daemon/service can be linked to a DNS daemon/service.

In reply to a post by jchamier:

it is interesting the router designers actually bothered to do it!

It is a convenient feature. From my point of view it negates the need to set the device's LAN IP address as reserved in the router, since I can always reference the device by name even if the LAN IP address changes.

In reply to a post by Oliver341:

It is a convenient feature.

Agreed, its why we build corporate systems that use DDNS.

But for many parents whom want to time lock their kids devices, or content filters etc, often only the IP is the constant.

But good on Sky as this may keep working when the MAC changes, as newer Android/iOS/Windows/Mac devices now implement by default.

In reply to a post by jchamier:

But good on Sky as this may keep working when the MAC changes, as newer Android/iOS/Windows/Mac devices now implement by default.

Yes, as I understand it the Sky router uses the hostname sent by the device's DHCP client to create the DNS record. This would be the same regardless of MAC address randomisation as long as the device does not randomise its hostname too!

In reply to a post by jchamier:

In reply to a post by Oliver341:

Yes, automatic. The router also creates DNS records for smartphones connected to it

Its quite easy to do with open source software on Linux, but it is interesting the router designers actually bothered to do it!

At least a couple of the popular DNS forwarders that are used by the various Linux based consumer routers just have it built in (some of them also handle the DHCP side in the same daemon).

In reply to a post by Oliver341:

Yes, as I understand it the Sky router uses the hostname sent by the device's DHCP client to create the DNS record.

Yes, and that's how it works in corporate systems, when laptops move around the company's buildings the IP address changes, and as DHCP provides the new address, the DNS gets updated automatically.

This would be the same regardless of MAC address randomisation as long as the device does not randomise its hostname too!

I'm unclear how android devices are named, but macOS, Windows, Linux and iPhone/iPad are quite easy, and the name doesnt' change.

In reply to a post by jchamier:

In reply to a post by Oliver341:

Yes. Here I am querying my router's DNS server directly for the hostname of one of my PC's on the network:

And on my Asus, I get:
*** No internal type for both IPv4 and IPv6 Addresses (A+AAAA) records available for <hostname>.

All my Asus routers resolve internal IP's to hostnames and vice versa with an nslookup.

If you go to System Log / DHCP Leases, then you can see all the LAN devices connected and which ones have hostnames set.

Maybe it requires hostname and domain name to be set in the Asus for this to work (under LAN / LAN IP). It's a setting I always configure.
Not all devices have a hostname configured but any that are missing can be added via the DHCP manual assignment option

In reply to a post by j0hn83:

All my Asus routers resolve internal IP's to hostnames and vice versa with an nslookup.

Ahh interesting. My AC-AX88U isn't currently.

If you go to System Log / DHCP Leases, then you can see all the LAN devices connected and which ones have hostnames set.

Yeah, I have some devices with static MAC to IPv4 mapping set up.

Maybe it requires hostname and domain name to be set in the Asus for this to work (under LAN / LAN IP). It's a setting I always configure.

I don't have a domain, so I will do some research, maybe an invalid.local in my future.

In reply to a post by j0hn83:

All my Asus routers resolve internal IP's to hostnames and vice versa with an nslookup.

I now have this working, and its really simple when you know. Thank you!