IP (v4/v6) connectivity setup in LTE modems

Bjørn Mork bjorn at mork.no
Wed Jan 31 12:19:01 UTC 2024

Aleksander Morgado <aleksandermj at chromium.org> writes:

> Hey all,
> I wrote a doc explaining how IPv4/IPv6 connectivity in LTE networks is
> setup (a very basic case scenario), including different possible
> interactions between host, modem and network, and focusing on how all
> these are exposed by ModemManager.
> It has been very useful for me to understand different IPv6 SLAAC
> scenarios that we have seen with different modem types, so I'm sure it
> will also be useful for others. Please take a look and report errors
> if any!
> https://modemmanager.org/docs/modemmanager/ip-connectivity-setup-in-lte-modems/

That's a very nice writeup!  Thanks.  Don't know how I missed it

I never knew of the extremely interesting IPv6 differences between
Qualcomm and "Intel" modems.  Guess I've been a littly too focused on
Qualcomm modems every sicne the big EM7345 disappointment.  Made me
wonder if I would have had more success with an "Intel" modem for my
DHCPv6-PD experiments.  IIUC, they tunnel link-local directly from the
host to the network?  Or is that only for RAs or specific link local

FWIW, I never figured out how to do DHCPv6-PD with the Qualcomm modems I
used for testing.  There's probably some magic trick.  I can obviously
work around the problem by using a non-link-local address for the DHCPv6
server.  But being able to directly address a link-local address on the
network side from the host would have made it so much easier, and
direcly comparable to a FTTH or xDSL configuration.

I guess I should dig out my old EM7345 and see how that works.  Although
it is pretty much irrelevant as I need to make this fly with Qualcomm
modems too.


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