https://bugzilla.novell.com/show_bug.cgi?id=436857
User aron.ujvari@microsec.hu added comment
https://bugzilla.novell.com/show_bug.cgi?id=436857#c3
--- Comment #3 from Aron Ujvari 2008-12-11 04:38:01 MST ---
I think, abosolutely yes. There are many use cases where a dummy interface can
makes life easier. Nowadays these are VPN, load balancing, failover or just
simple networking issues, ex. just need some more "real" network interfaces.
Personally I use dummy interface for load balancing and failover
implementation. I have two servers that acts as a load balancer. To do
balancing I need a director who forwards requests to the balancer servers. As I
have only two machines one of them have to be the director server also at a
time. But I need failover too, so I have to move this director function to the
other server in case of failure.
Using direct routing LVS server for load balancing requires that each balancer
servers have the service IP configured. On the other hand for the director
functionality I also have to configure this service IP on the servers as they
do failover for this function, but only on one of them at a time. This two
requirement is just the opposite, can't be fulfilled at the same time. At least
not on one interface.
On my public interface I do the failover, and only one public interface has the
service IP address configured. Meanwhile on the dummy interface, that have ARP
disabled in sysctl, I have the service IP configured all the time on all the
servers.
Technically this probably also be able to work on the loopback interface, but
then I had to mix two functionality on the loopback interface and I prefer to
avoid that if possible. Loopback interface is primarily for serve data packets
that really loops back to the server. I wouldn't like to change it's
configuration just to serve as a silent interface of the service IP. The
loopback interface is an important part of the system so it is the best not to
hack it while it is working well. Not even YaST is capable to configure it.
With dummy interface I can move this latter functionality to an other interface
where it won't interfere with other functionality and I would be able to use
YaST to make this setup if it had been configured well on boot. This way the
the failover and load balancer configuration (on the same machine) is not a
hack, but it's clean and correct from the administrator's perspective.
Moreover, regardless of that it is useful or not YaST has dummy interface
handling capability, but it is not working well. As long YaST has this
functionality the current behaviour is definitely a bug in my opinion. And as I
mentioned this functionality can be really useful probably not for most of the
users but for some experienced ones for sure.
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