static IP & DHCP problems on LAN

[Adam Funk]

On 2013-03-12, compdoc wrote:

>>the machine (desktop & home "server") has gone off its static IP address
> and onto a DHCP address from the router
>
> That's the problem with static IPs - when there are changes to the lan, the
> static settings have to be checked and changed manually if need be. IP
> address conflicts are common using static, and can cause really odd
> behaviors for the two PCs that are conflicting. With DHCP, you make a change
> at the server when needed and all clients get updated. And no conflicts.

I only have one thing with a static IP on the LAN now.

I think the problem was with the router firmware upgrade.  I
reinstalled the previous version of the firmware yesterday evening, &
everything has been fine this morning.


>> which makes it impossible for me to SSH into it (unless I can guess the IP
> address correctly)
>
> Not knowing what you are specifically referring to, it's likely this can be
> easily fixed. DNS might work.

If I'm inside the LAN, I ssh to the fixed IP address.  If I'm outside,
I ssh to a no-ip.com hostname, and the NAT router forwards the port to
the fixed LAN IP address.  (There's no way to do the port forwarding
on my equipment without a static LAN IP.)


>>I also tried running the '/etc/init.d/networking restart' command today, &
> that screwed up graphics & lightdm
>
> That command is the one I've used for years across several versions of
> Ubuntu with no issues. You saw this occur at the console?

Yes, I was in an xterm and it went into "low graphics mode" or
something like that.  Running 'sudo /etc/init.d/lightdm restart' from
a virtual console wouldn't bring up the GUI login screen until after I
rebooted.

>
>
>>#auto ath0
>>iface ath0 inet dhcp
>>
>>#auto wlan0
>>iface wlan0 inet dhcp
>>#v-
>>
>>I have no idea why it has ath0 and wlan0 stanzas --- I didn't type them in.
> That machine has only ever had one RJ45 network connection.
>
> Those seem to be wifi interfaces. If you have none, I would comment those
> out. (disable) Maybe you had a wifi card at some point?

No, but I did install Ubuntu on that machine something like 5 years
ago & I've been upgrading ever since.