LARTC - Mar 2002 - RE: question re: dead gateway detection

> > So my question is: is there some way that I can detect that the actual
> > route to the net is unusable, even though the gateway is up ? If not,
when 
> > either one of the lines is down, users will notice they''re
not getting a
> > connection randomly, depending on what gateway is used for that 
> > connection.
> > 
> > Thomas
I would assume the rest of your network would be running some kind of route
monitoring protocol (OSPF, RIP, etc).  Could you not just run gated and
listen in?  That would be the easiest way IMO.  Lots of info on the subject,
google is your friend.  HTH.

******************
Tom Steele
Comm/Systems Engineer
Children''s Hospital
Omaha, NE

Thanks for some of the hints.
> > > So my question is: is there some way that I can detect that the
actual
> > > route to the net is unusable, even though the gateway is up ? If
not,
> when 
> > > either one of the lines is down, users will notice
they''re not getting a
> 
> > > connection randomly, depending on what gateway is used for that 
> > > connection.
However, my basic question hasn''t been answered, and to put it simply :
is
there some way a user-space program can signify the dead gateway code to 
mark one of the gateways as dead or alive ? That would make this the 
easiest.

It''s not that it''s especially hard to write daemons to check
routes to
then change networkconfigurations on the fly, but it''s not the cleanest
solution IMO ;)

And on another note, I''m using iptables to DNAT on my firewall.  Now,
an
unintended side effect is that for web servers (maybe others as well), 
traffic now seems to come from the firewall instead of the actual outside 
ip address.  Is there some way I can get the real ip address to the server 
? I used to do ip-based blocking but that''s pretty ineffective now ;)

Thanks,

Thomas

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