Re: [lwip-users] dhcp_release_and_stop() clears the assigned IP address

[address@hidden]

Am 13.02.2019 um 22:17 schrieb R. Diez:
> > [...]
>
> > No, a private scanning tool using broadcasts...
>
> By private you mean not open sourced here?
>
> In any case, how can this tool help? If the device is not getting any IP 
> address over DHCP, and they do not have any fall-back IP, then they are not 
> reachable. Or do you mean the devices reset their IP address when they receive 
> a particular? That does not seem very robust. How do you implement security 
> then? And the users needs a custom tool, because I assume that this is not a 
> standard solution.

Yes, a custom tool is required. That's the downside. There are 
standardized protocols for "niches" like Profinet, however.

> > What fallback IP is that?
> > [...]
>
>
> The user enters an appropriate fall-back IP during device commissioning, next to the 
> "enable DHCP" option. No need to panic or assume anything nasty.

Ehrm, how do you reach the device for commissioning? Via DHCP or via 
fallback-IP? ;-)

So if the user has to enter an IP address, why use DHCP?


> Even if all devices have the same fall-back IP, that does not really matter, as 
> long as it is on a different subnet
or it is a reserved IP for that purpose.

It does. You'll get bogus result trying to reach such devices.

>Networks should still operate correctly if a client device IP is 
duplicated.

Network yes. IP communication won't.

>
 If the DHCP server is down, and the devices need it, you have bigger 
problems anyway. The fall-back IP is mainly designed so that you can 
easily isolate a device and access it with a minimum of fuss.

That's what AutoIP was invented for...

Regards,
Simon