On Tue, 2009-03-31 at 12:02 -0700, Kevin Keane wrote:
> Steve Polyack wrote:
> > Kevin Keane wrote:
> >> Inquiring minds want to know: why would you want to control the 
> >> source address? Doesn't the routing table automatically select the 
> >> correct one based on the destination address you want to reach?
> >>
> >>   
> > The OS is supposed to choose a "functional" address, which when paired 
> > with a routing entry, makes the destination reachable.  However, in a 
> > multi-homed environment this may not choose the desired connection 
> > (does not account for bandwidth, latency, hops, etc).  Few applications
> In all honesty, I'm not yet following (and the links you added went to a 
> 404 page, sorry ). 99% of the time when somebody comes up with an 
> unusual request like that, there is something for me to learn, so I hope 
> you can forgive me for probing further!
> 
Forgive me too..

> Do you mean, multihomed on the same physical network? Or multihomed on 
> two separate physical networks? On the same physical network, I could 
> see some merit if you have two NICs. Dedicating one NIC to bacula 
> traffic may allow a switch to establish a completely separate data path 
> and not impact regular traffic. But even then - shouldn't this be better 
> done as a second subnet overlayed over the same physical network?
> 
I guess a toy example can be cluster configurations: several resources
with different virtual ip and different volume groups, logical volumes,
file systems. Usually (Sun Cluster o RH Cluster Suite) vips are
associated to virtual interfaces (eth0:1, nge0:1,ecc.) on the same
subnet. If you want to backup a resource you can specify the ip for
binding bacula-fd and source address for each resource. 
Before this discussion I didn't realize I need to bind source address, I
supposed the communication flow to be director -> client -> sd.
Maybe source address binding helps with firewall rules definition..



> If it is multihomed on different physical networks, and the routing 
> table selects a suboptimal route, shouldn't you fix the routing table, 
> since these problems aren't really bacula problems?
> > There are also several situations in which the backup servers or 
> > clients may use additional IPs to establish network presence on a 
> > service-by-service basis (i.e. all bacula/backup traffic moves over 
> > one IP address, all web traffic over another IP address, all SSH/mgmnt 
> > over another address, etc etc).
> That makes sense for the destination IP. How does the source address 
> figure in this picture?
> > There was a big discussion about this some time ago which you may read:
> > http://www.mail-archive.com/bacula-us... AT lists.sourceforge DOT 
> > net/msg15640.htm 
> >
> > http://www.mail-archive.com/bacula-us... AT lists.sourceforge DOT 
> > net/msg15776.htm 
> >
> >
> 
> 


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