query-source for multiple interfaces

[Mark Andrews]

> In article <e4feh9$12k9$1 at sf1.isc.org>,
>  Sam Wilson <Sam.Wilson at ed.ac.uk> wrote:
> 
> > Looking at the ARM the "query-source" option seems to be able to specify 
> > only one address.  We are investigating anycast DNS on multihomed 
> > servers.  It looks as though I can't use "query-source" to allow queries 
> > to be sent from any address except the multicast address.  Is this true 
> > and is there any obvious workaround?  I've already thought of adding a 
> > second local /32 address that's specific to the box and sourcing the 
> > queries from there, but that's getting rather messy.
> 
> If the anycast address is an alias IP, I don't think you need to do 
> anything.  I think the OS will automatically default the source address 
> to the primary IP of the outgoing interface rather than an alias.
> 
> -- 
> Barry Margolin, barmar at alum.mit.edu
> Arlington, MA
> *** PLEASE post questions in newsgroups, not directly to me ***
> *** PLEASE don't copy me on replies, I'll read them in the group ***

	Also it does not make sence to send queries from a anycast
	address as the replies are not guarenteed to go back to the
	correct instance.

	For local anycast the you can sometimes get away with it
	if the load balancer / router has enough smarts to get the
	reply to the right instance.  Even then you it need to map
	both UDP and TCP connections to the same instance.

	Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org