Host data interface IP configuration via DHCP vs via control channel.

Bjørn Mork bjorn at
Thu Nov 10 09:47:08 UTC 2022

Arjen Smit <smit.arjen at> writes:

> This question actually does extend to IPv6, here also via the available
> control protocol (QMI/AT/etc) the connection is initiated.  It is the modem
> firmware that runs a SLAAC client process to receive a /64 prefix.  Then
> the data interface on the host is able retrieve that prefix (via a
> SLAAC/DHCPv6 client procedure (depending on the modem firmware
> capabilities) from the modem. Also here the alternative option exists to
> retrieve the IPv6 prefix (+ other items like Ipv6DNS, MTU size, or even PD
> - (e.g quectel AT+QIP6CFG="PD_addr") via the control interface from the
> modem and apply the result to the data interface.
> What is the modem manager approach in this ? It looks like always the data
> interface needs to use DHCP/SLAAC kind of client processes. As I prefer to
> be independent of specific modem firmware (DHCP) server processes (which
> are often outdated/have limited DHCP options supported) I am interested to
> understand  the pros/cons of the above approach (and the modem manager
> support of this approach).

I'm extremely interested in generic solutions to this problem.  My
understanding is that we can only make one side of the client <-> network

If you want to use DHCPv6 agaist a generic network, then you depend on a
specific modem firmware implementation.  There is no way for MM to
inject link local packets on the gtp link.  And there is no universal
proxying/relaying of DHCPv6 in modem firmware.  Is this correct?

If correct, which modem firmwares and methods are there supporting

That Quectel command looks very promising.  But are there similar
solutions for e.g Sierra Wireless modems?  Others?

Using routed DHCPv6 wrapped in DHCPv6 relay-forward messages would allow
a generic client solution regardless of modem firmware. But it becomes
very network dependent since you'd need a co-operating PGW and

Interesting in hearing about such deployments, if anyone knows of one.

Generally:  Are there anyone actually using DHCPv6-PD on a mobile
network? I.e outside the lab. How do you do that?


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