Re: DHCP and static IP configuration hangs when no DHCP

[Francesco Giudici <fgiudici redhat com>]

Hi David,

On 6/12/19 8:17 PM, David Bourgeois wrote:
> The only hack I found is to create a static IP only, then in add a 
> up-post script that manually launches dhclient on the interface. That 
> does what I need but it's somehow cumbersome.
>
> On Wed, Jun 12, 2019 at 8:15 PM David Bourgeois <david jaguarondi com 
> <mailto:david jaguarondi com>> wrote:
>
>     Hi Francesco,
>
>     Thank you for your answer. I can indeed do that to keep DHCP trying
>     forever or nearly, that's a good idea. But my problem is that the
>     static IP is not created at all until there's an answer from a DHCP
>     server. I was expecting that the static IP would be created then the
>     dynamic IP would appear whenever the DHCP answers. But they both
>     appear only when the DHCP answers. i'm unable to create a static IP
>     first, then start DHCP. Any idea?

This is weird, as I just gave it a try and works by assigning the static 
ip first, then keeping trying the dhcp. If the dhcp timeouts, the 
connection fails and is teared down, clearing also the static ip that 
was configured. This is why the trick worked for me.
Which NM version do you have?
Can you confirm that when the connection is in the "connecting" state 
(check with 'nmcli connection') the ip address is not assigned (check 
for the ip with 'ip add')?

Thanks

Francesco


>     Thanks,
>     David
>
>     On Wed, Jun 12, 2019 at 10:26 AM Francesco Giudici
>     <fgiudici redhat com <mailto:fgiudici redhat com>> wrote:
>
>         Hi David,
>
>         On 6/11/19 12:24 AM, David Bourgeois wrote:
>          > Hi,
>          >
>          > I can't find the proper configuration to have an always
>         enabled static
>          > IP address and an optional DHCP address when connected to a
>         network that
>          > has a DHCP server. My use case is a portable device that
>         connects to
>          > local embedded devices using a private local LAN so the
>         static IP should
>          > always be there. When we need to connect on the internet, I
>         would like
>          > to plug a DHCP enabled connection to the switch and receive a
>         second IP
>          > automatically from DHCP for this.
>          >
>          > I can setup both DHCP and static using this configuration:
>          > [ipv4]
>          > address1=10.192.11.10/16 <http://10.192.11.10/16>
>         <http://10.192.11.10/16>
>          > method=auto
>          >
>          > The problem is that the whole connection profile will fail if
>         no DHCP
>          > server is found, the static IP will never be set. As soon as
>         I plug the
>          > DHCP network, both IP will appear. But I would need the
>         static IP to be
>          > available from the beginning. I have the same problem if I
>         try the
>          > ifupdown configuration through /etc/network/interfaces. I had
>         gentoo in
>          > the past and could achieve this using their RC system, DHCP
>         would be
>          > assigned to eth0:0 and a static IP to eth0:1. I just can't
>         find a way to
>          > do this with Network Manager.
>          >
>          > Any idea if that's possible with the profile configuration,
>         or if I need
>          > to use 2 configurations or play with some scripts?
>
>         I think you can achieve your desired configuration by setting
>         the dhcp
>         timeout value to something really big.
>         As easy as:
>
>         $ nmcli connection modify $YOUR_CONNECTION_NAME
>         ipv4.dhcp-timeout infinity
>
>         This way, the connection will keep trying getting an ip from
>         time to
>         time, and will never be teared down.
>
>         Francesco
>
>          >
>          > Thank you,
>          > David
>          >
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