Re: Simultaneous use of link-local + DHCP for IPv4


On Wed, 2022-11-02 at 11:39 +0100, Christian Eggers wrote:
According to Wikipedia [1], IPv6 hosts are required to always
configure a
link-local address, even if a global address is available. As far as
know, NM allows only one type of address (link-local / DHCP / manual)
for an
IPv4 connection (although multiple addresses may be configured in
manual mode).

Would it be useful (or is it already possible), to allow parallel use
link-local + dhcp/manual for IPv4?

Background: On our (embedded) product, we currently implement only
IPv4 (nobody
asked for IPv6 support yet). The user is responsible for choosing the
selection method according to his needs in order to communicate with
our device.

In future versions, we would like to add peer-to-peer communication
our devices which shall work independently of a proper IP address
by the user. So if the device is configured for DHCP (factory
discovery and communication between our devices shall work also for
such cases,
where no DHCP server is present.

We try to avoid the "Microsoft" approach where link-local is used as
a fallback
if no DHCP server is responding. This would increase startup time and
perform well if the DHCP server is connected later (due to the mobile
nature of
our equipment).



Since 1.40, you can configure `` property. Try that.

One problem is that if you use DHCP + link-local, then the "activated"
state will not be reached before we get an DHCP and link-local address.
And the timeout for link-local addresses is rather high.


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