[Gllug] Debian gateways

[Bruce Richardson]

On 1/31/02, 10:52:24 AM, "Jackson, Harry" <HJackson at colt-telecom.com> wrote 
regarding RE: [Gllug] Debian gateways:


> > -----Original Message-----
> > From: Bruce Richardson [mailto:itsbruce at uklinux.net]
> >
> > They are if you didn't add the route any other way.  The
> > interfaces file
> > is read when the ifup and ifdown commands are executed, so
> > changing the
> > file has no effect until then.

> It has become a habit for me execute these commands when I play with the
> network set-up. It is not always required but I always feel better after 
I
> have done them.

If you want to test how much you are learning about networking, try not 
doing that immediately.  Instead, when you want to make a change to an 
interface try making just that change (with route, ifconfig or whatever). 
 Look at the results, see if they are what you were after and compare 
them to what happens when you do do ifdown;ifup.  The 
/etc/network/interfaces construct is Debian-specific (and subject to 
occasional change) while the route, ifconfig and ip commands are standard 
across distributions (and vital if you're going to try and troubleshoot).

There are also situations where bringing interfaces up and down is 
inappropriate.  For example, at work I have a multi-homed host acting as 
gateway to our several routes out.  It has 4 interfaces, each with extra 
rules (policy routing and other things) attached that are triggered when 
an interface is brought down or up.  When our adsl line goes down I need 
to switch the default route from the adsl interface to the leased line 
and tweak a couple of rules.  Altering the interfaces file and bringing 
interfaces down and up isn't an option.

-- 

Bruce

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