dhcpcd: raw-ip support

Bjørn Mork bjorn at mork.no
Mon Aug 19 08:49:34 UTC 2019

Yegor Yefremov <yegorslists at googlemail.com> writes:

> I have a project where I'm using dhcpcd client. It is working without
> any problems with older modems like Quectel UC20 etc. But now we want
> to switch to SIM7600G-H and it is working in raw-ip mode. So far only
> udhcpc can handle such MAC address-less interfaces.
> Do you know what is so special about udhcpc compared to other DHCP
> clients?

It's mostly L2 agnostic, meaning that it will work on non-ethernet

"Fixing" this for other clients isn't really that hard, if required. I
did this proof-of-concept for ISC dhclient for example:


> Is there any raw-ip related documentation?

Not really. Just delete "ethernet" from other documentation :-)

The only difference is that the ethernet header is removed from the
packets between host and modem.  It is not replaced by anything.

We could have made up a new "ARP hardware type" for this, but I didn't
see much point.  The "hardware type" is simply no header and no
address. So I went with the example from the tuntap driver, using


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