IPv6 "bloat"

Matt Hoppes mattlists at rivervalleyinternet.net
Sat Mar 19 23:11:47 UTC 2022

I misspoke... it's not UUID... It's DUID.

This isn't a backend management issue.  This is a protocol issue.  The 
MAC of the interface needs to be sent with a DHCP request so that it can 
be properly authenticated to the physical device.

As long as the client and DHCPv6 server are on the same network 
interface -- it all works fine.  However, when you relay that 
information, you now lose the MAC address information.

Further, because the MAC is disconnected in IPv6 it becomes more 
difficult to make the connection between IPs on a dual-stack client.

Everyone prints the MAC (a unique ID on devices and devices packaging). 
Almost nobody prints the DUID on a device, so how do you pre-populate 
your DHCP server?  I can see that it encourages "one interface per 
network" and so encourages bonding, bridging or whatever, but is being 
able to differentiate the interfaces of a host really so bad? I can't 
help but feel that it would have been nice for DHCPv6 to send DUID and MAC.

On 3/19/22 7:03 PM, Michael Thomas wrote:
> On 3/19/22 3:56 PM, Matt Hoppes wrote:
>> On 3/19/22 6:50 PM, Michael Thomas wrote:
>>> On 3/19/22 3:47 PM, Matt Hoppes wrote:
>>>> It has "features" which are at a minimum problematic and at a 
>>>> maximum show stoppers for network operators.
>>>> IPv6 seems like it was designed to be a private network 
>>>> communication stack, and how an ISP would use and distribute it was 
>>>> a second though.
>>> What might those be? And it doesn't seem to be a show stopper for a 
>>> lot of very large carriers.
>> Primarily the ability to end-to-end authenticate end devices. The 
>> primary and largest glaring issue is that DHCPv6 from the client does 
>> not include the MAC address, it includes the (I believe) UUID.
>> We have to sniff the packets to figure out the MAC so that we can 
>> authenticate the client and/or assign an IP address to the client 
>> properly.
>> It depends how you're managing the network.  If you're running PPPoE 
>> you can encapsulate in that.   But PPPoE is very 1990 and has its own 
>> set of problems.  For those running encapsulated traffic, 
>> authentication to the modem MAC via DHCP that becomes broken.  And 
>> thus far, I have not seen a solution offered to it.
> I was honestly more interested in the bloat angle, but this sounds like 
> a backend problem of your own making most likely. But I'm not motivated 
> to see if it's actually the case or just a misunderstanding.

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