dhcpcd-discuss

Hi

Sorry for the late reply.

On 04/06/2014 22:35, David Hauck wrote:
> I've been researching various techniques for using DHCP configured
> interfaces in a multi-homed environment. Unfortunately, I haven't
> uncovered any clear guidance on the various aspects of this with
> DHCPCD. One particular question I have relates to all of the (DHCP)
> interfaces communicating with the same DHCP server and being
> subsequently served addressing information from a pool of addresses on
> the same subnet (e.g., 192.168.2.[234]/24). This isn't problematic in
> and of itself, but generally each exchange also includes any number
> of: hostname, gateway, name server, ntp servers, static routes,
> etcetera. I've seen some material that indicates interface-specific
> DHCP configuration can be used to control which interfaces ignore
> these duplicated, global settings and, correspondingly, which
> interface might be configured to accept them (e.g., to ensure only one
> negotiates the configuration for hostname, default gateway, name
> servers, etc.).
>
> I recognize that there might be some configurations where it *may* be
> desirable to have, for e.g., multiple default gateways, but even this
> is generally frowned upon (note that my current focus is IPv4).
> However, I'd like to constrain possibilities like this in my
> configurations.
>
> What is the recommended way to do this under a Debian-based (sysvinit)
> system? I saw a reference somewhere that mentioned using an
> /etc/default/dhcpcd file to help with something like this, but I don't
> think this is standard. I'm guessing there's something similar built
> into DHCPCD (i.e., some way to configure interface-specific
> parameters/environment variables), but I've not yet been able to
> isolate this.

The recommended dhcpcd way is just to run dhcpcd and let it manage 
things :)
Basically it will internally manage ip addressing and routing per 
interface.
On Linux there will be multiple default gateways, but this is *fine* 
because they are split out by routing metric (lowest wins).
In the typical multi-homed system (ie a laptop with ethernet and 
wireless) dhcpcd will automatically prefer the wired host rather than 
the wireless.
It should be a fairly seamless transition between the two as well 
(unplug / plug the wired cable)

As to information duplication, well all of the hook scripts take this 
into account.
So for resolv.conf and ntp{d}.conf it's all managed.
You may want to look into using resolvconf (I personally recommend 
openresolv ;) ) as that can handle it better than dhcpcd.

Thanks

Roy