query-source for multiple interfaces

Mark Andrews Mark_Andrews at isc.org
Wed May 17 23:49:12 UTC 2006

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

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