WiFi problem, loss of DHCP/DNS when changing from one SSID to another but OK from turn on

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WiFi problem, loss of DHCP/DNS when changing from one SSID to another but OK from turn on

Chris Green
I am having a problem with WiFi connections from my Lenovo laptop
running xubuntu 17.10.

I have a number of different WiFi sources round our rather rambling
house so the laptop has to move from one to another as I move around.

When moving to one SSID in particular it always fails to get proper
settings via DHCP, in fact it acts rather as if DHCP fails altogether.
Network Manager tells me I'm connected but the WiFi has no IP address
and thus, obviously, no functional connection.

If I turn the laptop off and power it up then it connects OK to the
same SSID.  If I just reset the laptop it *doesn't* connect
successfully.  Connecting to other SSIDs around the house doesn't seem
to suffer from the same problem, it's just one SSID where this
happens. (I'm pretty sure this is the case but I've not spent a very
long time checking).

I've found that if I do "nmcli off" followed by "nmcli on" (as root of
course) then I get a good connection again.  Disconnecting and
reconnecting from the Network Manager applet in the panel doesn't
clear the problem though.

Does anyone have any suggestions as to what might be wrong?

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Re: WiFi problem, loss of DHCP/DNS when changing from one SSID to another but OK from turn on

Chris Green
On Sat, Feb 10, 2018 at 07:51:00PM +0000, Chris Green wrote:

> I am having a problem with WiFi connections from my Lenovo laptop
> running xubuntu 17.10.
>
> I have a number of different WiFi sources round our rather rambling
> house so the laptop has to move from one to another as I move around.
>
> When moving to one SSID in particular it always fails to get proper
> settings via DHCP, in fact it acts rather as if DHCP fails altogether.
> Network Manager tells me I'm connected but the WiFi has no IP address
> and thus, obviously, no functional connection.
>
> If I turn the laptop off and power it up then it connects OK to the
> same SSID.  If I just reset the laptop it *doesn't* connect
> successfully.  Connecting to other SSIDs around the house doesn't seem
> to suffer from the same problem, it's just one SSID where this
> happens. (I'm pretty sure this is the case but I've not spent a very
> long time checking).
>
> I've found that if I do "nmcli off" followed by "nmcli on" (as root of
> course) then I get a good connection again.  Disconnecting and
> reconnecting from the Network Manager applet in the panel doesn't
> clear the problem though.
>
> Does anyone have any suggestions as to what might be wrong?
>
Just to add some further information running 'nmcli monitor' shows the
following for an unsuccessful connection:-

    Networkmanager is now in the 'disconnected' state
    wlp4s0: disconnected
    wlp4s0: connecting (prepare)
    wlp4s0: using connection '2860n'
    Networkmanager is now in the 'connecting' state
    wlp4s0: connecting (need authentication)
    wlp4s0: connecting (prepare)
    wlp4s0: connecting (configuring)
    2860n: connection profile changed
    wlp4s0: connecting (getting IP configuration)
    wlp4s0: connecting (checking IP connectivity)
    wlp4s0: connecting (starting secondary connections)
    wlp4s0: connected
    Networkmanager is now in the 'connected (local only)' state

whereas for a successful connection I see:-

    Networkmanager is now in the 'disconnected' state
    Networkmanager is now in the 'connecting' state
    wlp4s0: connecting (prepare)
    wlp4s0: using connection '2820n'
    wlp4s0: connecting (need authentication)
    2820n: connection profile changed
    wlp4s0: connecting (prepare)
    wlp4s0: connecting (configuring)
    wlp4s0: connecting (getting IP configuration)
    wlp4s0: connecting (starting secondary connections)
    wlp4s0: connected
    '2820n' is now the primary connection
    Networkmanager is now in the 'connected' state
    Connectivity is now 'full'

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Re: WiFi problem, loss of DHCP/DNS when changing from one SSID to another but OK from turn on

Ralf Mardorf-5
In reply to this post by Chris Green
On Sat, 10 Feb 2018 19:51:00 +0000, Chris Green wrote:
>Does anyone have any suggestions as to what might be wrong?

While nowadays networkmanager is held in high esteem, I anyway prefer
scripts for networking over any tool. I'm not using WiFi for a Linux
device, but I did use ADSL and I'm using DHCP connections by scripts
only. Apart from this, there were and probaply still are tools
available, that in my experiences worked and perhaps still work more
reliable, than at least oldish networkmanager releases. IOW if
something should go wrong when using networkmanager, my favorite
suspect still would be networkmanager.


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