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  • FIRST POST
    • esuhl
    • By esuhl 7th Sep 17, 7:38 PM
    • 7,534Posts
    • 5,327Thanks
    esuhl
    IPv6, DHCP and DrayTek router...?
    • #1
    • 7th Sep 17, 7:38 PM
    IPv6, DHCP and DrayTek router...? 7th Sep 17 at 7:38 PM
    I'm (still) trying to get my head round IPv6, and how to set it up on my DrayTek Vigor 2830n router.

    Until now, I'd disabled IPv6. But (for the sheer geekery) I want to understand and enable it.

    With IPv4, a WAN interface gets a public IP address, and NAT and DHCP are used to allocate private IPv4 addresses to local devices.

    But how does this work with IPv6? There are options to use DHCP with IPv6 on my router. So... do I only get one IPv6 address from my ISP and NAT/DHCP are still used on the LAN? Or does the DHCP server on my router just pass on the request to my ISP's DHCP server to allocate a new IPv6 address?

    Also, I understand that an IPv6 address can be associated with a device's MAC address (causing privacy issues), and that IPv6 devices can use randomly generated temporary IPv6 addresses. How do I enable that, and how does it work (via DHCP?)?

    Lastly, any tips for what settings I should enter on the router? What's RADVD, for example? Should I enable it on a simple home network?

    Screenshot: https://www.dropbox.com/s/x20jgn6xvmt69qz/DrayTek%20IPv6%20screen.PNG?dl=0

    (Oh, and does anyone know what Sky's IPv6 DNS servers are?)

    Thanks for any tips!
Page 1
    • I have spoken
    • By I have spoken 7th Sep 17, 8:38 PM
    • 4,963 Posts
    • 9,656 Thanks
    I have spoken
    • #2
    • 7th Sep 17, 8:38 PM
    • #2
    • 7th Sep 17, 8:38 PM
    > So... do I only get one IPv6 address from my ISP and NAT/DHCP are still used on the LAN?<

    If your ISP supports IPv6 then an IPv6 enabled router will generally ask for a delegation prefix, giving the first part of an IPv6 address. The router will then allocate full IPv6 addresses that make up a subnet based on the prefix. Most delegation prefix still allow for 1,000s of unique addresses in the subnet.

    TBH, you may be better swapping back the Sky hub and get IPv6 working with their kit. Unless the Draytek does DHCP-PD (Prefix Delegation) you may be out of luck.
    Last edited by I have spoken; 07-09-2017 at 8:55 PM.
    • AndyPix
    • By AndyPix 7th Sep 17, 8:49 PM
    • 2,690 Posts
    • 1,814 Thanks
    AndyPix
    • #3
    • 7th Sep 17, 8:49 PM
    • #3
    • 7th Sep 17, 8:49 PM
    IPv6 is the work of the devil .. and should be killed in it's sleep
    Running with scissors since 1978
    • esuhl
    • By esuhl 8th Sep 17, 2:11 AM
    • 7,534 Posts
    • 5,327 Thanks
    esuhl
    • #4
    • 8th Sep 17, 2:11 AM
    • #4
    • 8th Sep 17, 2:11 AM
    > So... do I only get one IPv6 address from my ISP and NAT/DHCP are still used on the LAN?<

    If your ISP supports IPv6 then an IPv6 enabled router will generally ask for a delegation prefix, giving the first part of an IPv6 address. The router will then allocate full IPv6 addresses that make up a subnet based on the prefix. Most delegation prefix still allow for 1,000s of unique addresses in the subnet.

    TBH, you may be better swapping back the Sky hub and get IPv6 working with their kit. Unless the Draytek does DHCP-PD (Prefix Delegation) you may be out of luck.
    Originally posted by I have spoken
    Ah, right. Thanks. Looking again at the manual, it looks like my router supports "prefix delegation", and that the router's DHCPv6 server is what makes that work.

    But I'm still a bit confused as to how temporary (as opposed to device-specific) IPv6 addresses are allocated. I guess the DHCPv6 server takes care of that too? :-/

    I might plug in the Sky router again to have a look at the settings.

    IPv6 is the work of the devil .. and should be killed in it's sleep
    Originally posted by AndyPix
    Better the devil you know.
    • dj1471
    • By dj1471 8th Sep 17, 4:45 AM
    • 824 Posts
    • 549 Thanks
    dj1471
    • #5
    • 8th Sep 17, 4:45 AM
    • #5
    • 8th Sep 17, 4:45 AM
    Your ISP will allocate a block of address to you, usually a /64. There are several different ways the router can pick this up from the ISP.

    The router will then advertise this prefix to all of your hosts who will generate an IPv6 address based on their MAC address. Again there are several different ways this can happen, DHCPv6 is common but not actually required if all you want to assign is an IP address.

    See SLAAC

    You don't need to use a DNS server over IPv6 to lookup IPv6 addressees.

    All you should need to do is enable IPv6 and DHCPv6 and everything should just work, assuming your hosts haven't got IPv6 disabled.

    Try http://ipv6test.google.com.
    • I have spoken
    • By I have spoken 8th Sep 17, 7:41 AM
    • 4,963 Posts
    • 9,656 Thanks
    I have spoken
    • #6
    • 8th Sep 17, 7:41 AM
    • #6
    • 8th Sep 17, 7:41 AM
    There's more advice over on the Sky support forums
    • spenderdave
    • By spenderdave 8th Sep 17, 8:25 AM
    • 407 Posts
    • 231 Thanks
    spenderdave
    • #7
    • 8th Sep 17, 8:25 AM
    • #7
    • 8th Sep 17, 8:25 AM
    Many non-Sky routers don't support the /56 prefix delegation that Sky and BT use. I tried to get my TP-Link router to work but it wouldn't so using the Sky SR102 which just works.
    • onomatopoeia99
    • By onomatopoeia99 8th Sep 17, 9:05 AM
    • 3,334 Posts
    • 7,360 Thanks
    onomatopoeia99
    • #8
    • 8th Sep 17, 9:05 AM
    • #8
    • 8th Sep 17, 9:05 AM
    IPv6 is the work of the devil .. and should be killed in it's sleep
    Originally posted by AndyPix
    NAT is evil and should never have been born

    I'd rather a protocol that allows every device to be uniquely addressable, than a bodge to overcome the 2^32 address limit that IPv4 imposes.
    INTP, nerd, libertarian and scifi geek.
    Home is where my books are.
    • John Gray
    • By John Gray 8th Sep 17, 1:10 PM
    • 5,010 Posts
    • 2,635 Thanks
    John Gray
    • #9
    • 8th Sep 17, 1:10 PM
    • #9
    • 8th Sep 17, 1:10 PM
    I'd rather a protocol that allows every device to be uniquely addressable,,,
    Originally posted by onomatopoeia99
    But what if you actually don't want your devices to be globally addressable?
    • dj1471
    • By dj1471 8th Sep 17, 1:23 PM
    • 824 Posts
    • 549 Thanks
    dj1471
    But what if you actually don't want your devices to be globally addressable?
    Originally posted by John Gray
    Why wouldn't you?

    You're behind a firewall, so...? All of your devices can already be uniquely identified using other means (cookies, browser UA string, etc etc).
    • onomatopoeia99
    • By onomatopoeia99 8th Sep 17, 2:30 PM
    • 3,334 Posts
    • 7,360 Thanks
    onomatopoeia99
    But what if you actually don't want your devices to be globally addressable?
    Originally posted by John Gray
    I cannot think of a reason why you would not want them to.

    NAT is not a firewall.
    INTP, nerd, libertarian and scifi geek.
    Home is where my books are.
    • AndyPix
    • By AndyPix 8th Sep 17, 2:42 PM
    • 2,690 Posts
    • 1,814 Thanks
    AndyPix
    No one can port scan all my devices that are NATted.


    With the IOT going the way that it is, and security not being the best on someones "internet connected toaster", i like the fact that most of my devices dont face the outside world.
    Running with scissors since 1978
    • onomatopoeia99
    • By onomatopoeia99 8th Sep 17, 5:54 PM
    • 3,334 Posts
    • 7,360 Thanks
    onomatopoeia99
    No one can port scan all my devices that are NATted.
    Originally posted by AndyPix
    No-one can port scan any of my devices that have uniquely identifiable addresses either, other than on the ports that I deliberately open on my hardware firewall.

    Edit - well they can, but they won't get past the firewall as it will just drop the packets.
    INTP, nerd, libertarian and scifi geek.
    Home is where my books are.
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