[TriLUG] Linux Host connectivity issue

[Matt Flyer via TriLUG]

On Wed, 2018-02-28 at 13:08 -0500, Ron Kelley via TriLUG wrote:
> Sounds like the wireless card is trying to get a DHCP address - thus
> using the interface as the default GW.  When the connection fails, it
> goes back to the onboard ethernet interface.
> 
> Any way to remove the wireless device?
> 
Ron, interesting thought and good suggestion.  In this particular case,
only the wired adapter was activated, but I do have to be careful to
not activate the wired and wireless devices simultaneously because
they're in different networks; only the wired is in the vlan.  That
causes the dual gateway syndrome and would have the same symptom.

On Wed, 2018-02-28 at 13:09 -0500, William Sutton wrote:
> what is the static vs dhcp situation?  is it possible that something
> else 
> is grabbing the same address via dhcp?
> 
> William Sutton

William, I think you may have hit the nail on the head.  I moved the PC
to a static address in a different octet of the vlan onto an address
that is reserved for my use.  The problem seems to have gone away as
I've run ping against the gateway for several minutes and haven't
dropped a packet.

I also noticed a couple of other interesting things.  One, I started
having the problem on Friday afternoon, it disappeared on Monday and
then came back yesterday and today.  Two, I set up two consoles to
ping, one to ping the gateway, the other to ping a local server
machine.  I noticed that I would lose both of them, but the local
machine was more reliable.  When they would both go down, the local
machine would come back a few seconds before the gateway.

It appears that something went screwy in the DHCP and either multiple
devices have the same address or someone statically configured a
machine with the same address.  I didn't think to record the address
that I had received from the DHCP but I could reset the network back to
DHCP, get an address, verify that it is broken, and then reconfigure
back to my static IP and see if I can ping the device on the DHCP
address.  I may even be able to run nmap against it to see if it is a
PC or some other sort of device that someone plugged in.