On Wed, 10 Jun 2015, David Jones wrote:
[One should run a caching DNS server on a mail server.]
My point was that running a local caching server is the only way one
can know exactly how the lookups are happening. If you point to a
DNS server that you don't manage, it could be forwarding to an ISP's
DNS caches which will aggregate your queries in with others and could
cause unexpected results for those RBLs that limit queries.
One other technical benefit to running a local caching server is that if
SA is configured to talk to it va the localhost (loopback) interface there
are MTU advantages.
Most loopback interfaces have a MTU of 16K (or bigger) and will handle large
UDP packets without fragementation. In general DNS transactions are fastest
via UDP if you don't have fragementation issues.
--
Dave Funk University of Iowa
<dbfunk (at) engineering.uiowa.edu> College of Engineering
319/335-5751 FAX: 319/384-0549 1256 Seamans Center
Sys_admin/Postmaster/cell_admin Iowa City, IA 52242-1527
#include <std_disclaimer.h>
Better is not better, 'standard' is better. B{
