Update release note for #1877

(cherry picked from commit bee9ed84f463ed599f91f119ed673b07d4d6fb81)

diff --git a/doc/notes/notes-current.rst b/doc/notes/notes-current.rst
index 0f06a8a5edb40e42de3439a0823014391b79c1b8..b05fb4d7e71846bb82c69f8fe1cb7c5f16e91949 100644 (file)
--- a/doc/notes/notes-current.rst
+++ b/doc/notes/notes-current.rst
@@ -37,8 +37,22 @@ Feature Changes
 
 .. _relnotes-9.16.4-bugs:
 
--  The default value of ``max-stale-ttl`` has changed from 1 week to
-   12 hours. [GL #1877]
+-  The default value of ``max-stale-ttl`` has changed from 1 week to 12 hours.
+   This option controls how long named retains expired RRsets in cache as a
+   potential mitigation mechanism, should there be a problem with one or more
+   domains.  Note that cache content retention is independent of whether or not
+   stale answers will be used in response to client queries
+   (``stale-answer-enable yes|no`` and ``rndc serve-stale on|off``).  Serving of
+   stale answers when the authoritative servers are not responding must be
+   explicitly enabled, whereas the retention of expired cache content takes
+   place automatically on all versions of BIND that have this feature available.
+   [GL #1877]
+
+   .. warning:
+       This change may be significant for administrators who expect that stale
+       cache content will be automatically retained for up to 1 week.  Add
+       option ``max-stale-ttl 1w;`` to named.conf to keep the previous behavior
+       of named.
 
 Bug Fixes
 ---------