Ipv6 dhcp



  • i'd like to make my internal lan ipv6 ready.
    i set up my lan interface with a static ipv6 fdf5:4d23:bbbb:92fe:0:0:0:1/96 and now i would like to configure the dhcpv6 server.
    to do that i set the range of the dhcpv6 server to fdf5:4d23:bbbb:92fe:0:0:0:f000 - fdf5:4d23:bbbb:92fe:0:0:0:ffff and when i set a static mapping of a host to fdf5:4d23:bbbb:92fe:0:0:0:4 it works nicely.

    but if i would like to give a host more that one ip, and therefore set the IPv6 address field of the static mapping to fdf5:4d23:bbbb:92fe:0:0:4:0/112, the dhcpv6 server seems to stop responding to dhcp client requests.

    am i doing something wrong?



  • Your address range is to small. You need at least a /64 to allow auto addres. Read RFC 4291 at https://www.ietf.org/rfc/rfc4291.txt .



  • Why do you want to use DHCP?  SLAAC works fine.



  • @JKnott:

    Why do you want to use DHCP?  SLAAC works fine.

    Can I give a fixed ip range to different devices with SLAAC?
    I need to go read some docs on SLAAC.


  • LAYER 8 Netgate

    Can I give a fixed ip range to different devices with SLAAC?

    No.



  • @Derelict:

    Can I give a fixed ip range to different devices with SLAAC?

    No.

    Ok, back to dhcp then. I will try to increase the address range and see if I can hand out a /112 to each host


  • LAYER 8 Netgate

    That is not how it works.

    Get a tunnel from www.tunnelbroker.net and a /48 and do it right.



  • @Derelict:

    Can I give a fixed ip range to different devices with SLAAC?

    No.

    Actually, you can.  Just assign a MAC address to whatever you want and the MAC based SLAAC will follow.



  • @pox:

    @Derelict:

    Can I give a fixed ip range to different devices with SLAAC?

    No.

    Ok, back to dhcp then. I will try to increase the address range and see if I can hand out a /112 to each host

    Why a /112?  Normally, a network has a /64.  If all you want to do is experiment and don't need Internet access, you can use Unique Local Addresses. This provides a /48 that you can play with all you want.  If you do need Internet access, then you can use a tunnel, as suggested above, if your ISP doesn't provide IPv6.


  • LAYER 8 Netgate

    @JKnott:

    @Derelict:

    Can I give a fixed ip range to different devices with SLAAC?

    No.

    Actually, you can.  Just assign a MAC address to whatever you want and the MAC based SLAAC will follow.

    That is capital-U Ugly.



  • @Derelict:

    @JKnott:

    @Derelict:

    Can I give a fixed ip range to different devices with SLAAC?

    No.

    Actually, you can.  Just assign a MAC address to whatever you want and the MAC based SLAAC will follow.

    That is capital-U Ugly.

    Perhaps, but I'm more interested in why DHCP is required.  I get the impression from the posts that the OP isn't quite sure about what he's doing.  With the /112 prefixes, he's doing something even more "ugly".  If he wants multiple networks, then he should get a decent size prefix from an ISP or tunnel, or use ULA to create his own /48.

    One thing I've noticed is a lot of people are stuck in the IPv4 mindset, where addresses are scarce.  They have a problem considering how that problem doesn't exist with IPv6.



  • @JKnott:

    @pox:

    @Derelict:

    Can I give a fixed ip range to different devices with SLAAC?

    No.

    Ok, back to dhcp then. I will try to increase the address range and see if I can hand out a /112 to each host

    Why a /112?  Normally, a network has a /64.

    That's for a host, not a network. I would like to give one host 65536 addresses via dhcp (or any other centrally managed way would be ok too).
    Or am I missing something obvious here?



  • @JKnott:

    @Derelict:

    @JKnott:

    @Derelict:

    Can I give a fixed ip range to different devices with SLAAC?

    No.

    Actually, you can.  Just assign a MAC address to whatever you want and the MAC based SLAAC will follow.

    That is capital-U Ugly.

    Perhaps, but I'm more interested in why DHCP is required.  I get the impression from the posts that the OP isn't quite sure about what he's doing.  With the /112 prefixes, he's doing something even more "ugly".  If he wants multiple networks, then he should get a decent size prefix from an ISP or tunnel, or use ULA to create his own /48.

    One thing I've noticed is a lot of people are stuck in the IPv4 mindset, where addresses are scarce.  They have a problem considering how that problem doesn't exist with IPv6.

    You are right that I am not sure of what I am doing :) I am playing with ipv6 and trying to understand how the pieces fit together.


  • LAYER 8 Netgate

    What I tell people is to stop thinking about the 64 host bits entirely. To you they don't exist.

    If you get a /48 you can assign 65536 /64 networks out of it. If you have a /56, 256 networks. A /60, 16. The 64 host bits simply do not exist.

    Work in /64s. Save the subnetting longer than that for when you know you need it and can say why.



  • @Derelict:

    If you want a host with 65536 addresses on it (good luck with that), just route a /64 to it.

    While you might be able to coerce DHCP6 to do a /112 prefix delegation, why would you?

    Or just pick a /112 range out of the /64 on the interface and assign them statically.

    IPv6 doesn't do much to allow more hosts in one broadcast domain. 64K addresses is still not going to work very well if at all.

    Maybe if you disclose what you are trying to do a better solution can be devised.

    Sure: i have my internal lan with some servers. On one server, say hostname fritz, I have an ssh server, an http server that hosts 3 websites and an imap server.
    I would like to publish all those services on the LAN with their own ip. So say
    ssh server fdf5:4d23:aaaa:bbbb:0:0:0:1:22
    website 1: fdf5:4d23:aaaa:bbbb:0:0:0:2:80 + 443
    website 2: fdf5:4d23:aaaa:bbbb:0:0:0:3:80 + 443
    website 3: fdf5:4d23:aaaa:bbbb:0:0:0:4:80 + 443
    imap server: fdf5:4d23:aaaa:bbbb:0:0:0:5:993

    How should I do that? Is there a best practice? Hardcoding the addresses on the host fritz does not seem right to me, because if someone else on the lan uses the same addresses I have a conflict.
    I thought I could use the dhcpv6 to assign host fritz a /112, so host fritz knows he can use those addresses however he pleases, without having to worry of using someone else's addresses.
    Is my reasoning wrong? Should I just hardcode the addresses on the server and be done with it?


  • LAYER 8 Netgate

    I would. Otherwise you have to worry about the addresses changing and updating DNS for all your hosts.

    If you want to run servers you have to manage IP addresses. IPv6 doesn't change that.



  • That's for a host, not a network. I would like to give one host 65536 addresses via dhcp (or any other centrally managed way would be ok too).
    Or am I missing something obvious here?

    Yes.  While IPv6 supports multiple IPs on an interface (mine currently has 17) I suspect 65K is a bit much.  If you're running virtual machines for those servers, they will get there own individual addresses, if configured to bridge.


Log in to reply