Bringing the Ethernet Interface Down for a While

Bringing the Ethernet Interface Down for a While

[Martin G. McCormick]

	I am using Debian Linux on a system connected to DSL.
I recently had the idea of temporarily taking the
Ethernet connection down for periods of time when network access is not
needed.  One could use cron or at to do the ifconfig eth0 down at
one time and then bring it back up with ifconfig eth0 up at some
other time.

	What happens is that the ifconfig eth0 down and ifconfig
eth0 up commands both work normally but the system can't seem to connect
to remote hosts after the interface comes back up.  Attempts to
use ssh get the "name or service not available." error messages
and attempts to ping remote hosts give a "network is unreachable"
error.

	What else should I be looking at to restore
functionality?

	This isn't an urgent situation, but my curiosity is up
now since everything looks good but something doesn't return to
normal when the Ethernet interface is brought back up.

Martin McCormick WB5AGZ  Stillwater, OK 
OSU Center for Computing and Information Services Network Operations Group

Re: Bringing the Ethernet Interface Down for a While

[Frank Carmickle]

Why you would want to do this is beyond me.  Hell you could join kirk's
seti group!  Anyway the reason is you need to add the default route after
bringing the interface up.

If you are doing this because you are worried about security I suggest you
get yourself a firewall.  Bringing the interface down for a time only
helps during those times obviously.  

On Wed, 3 Oct 2001, Martin G. McCormick wrote:
> eth0 up commands both work normally but the system can't seem to connect
> to remote hosts after the interface comes back up.  Attempts to

-- 
     Frank Carmickle
phone:     412 761-9568
email:     frankiec@dryrose.com

Re: Bringing the Ethernet Interface Down for a While

[Kirk Wood]

I would use the scripts for doing this that the system uses when booting
or shutting down. The format would be "/etc/init.d/networking stop" and
"//etc/init.d/networking start". But perhaps there is yet another way.

=======
Kirk Wood
Cpt.Kirk@1tree.net

"When I take action, I'm not going to fire a $2 million missle at
a $10 empty tent and hit a camel in the butt. It's going to be decisive."
	- President George Bush

RE: Bringing the Ethernet Interface Down for a While

[Whitley GS11 Cecil H]

Hi,
Hmmmm, sounds to me like a dhcp issue.  If your service is like roadrunner
here, they timeout the ip address every four hours.  I've not used dhcp
under linux, but I think if you do a renew things will come back to normal.

Anyone out there got the command specifics for a release/renew for dhcp
under linux?
ifconfig eth0 renew
That would be my guess, but it's just a guess.  All the unix boxes i've
worked with have static addresses.  

Cecil

Re: Bringing the Ethernet Interface Down for a While

[Jason]

actually.... just looked at the man page for dhcpcd:
it would be

dhcpcd -n

to renew your lease



> Anyone out there got the command specifics for a release/renew for dhcp
> under linux?
> ifconfig eth0 renew
> That would be my guess, but it's just a guess.  All the unix boxes i've
> worked with have static addresses.