correct RFC3484 address selection caveat (#2407)

and move it to a more prominent location

Fixes #1710

site/weavedns/how-works-weavedns.md

@@ -17,18 +17,6 @@ When weaveDNS is queried for a name in the `.weave.local` domain, it
 looks up the hostname in its memory database and responds with the IPs
 of all containers for that hostname across the entire cluster.
 
-###Basic Load Balancing and Fault Tolerance
-
-WeaveDNS returns IP addresses in random order to facilitate basic
-load balancing and failure tolerance. Most client side resolvers sort
-the returned addresses based on reachability, and place local addresses
-at the top of the list (see [RFC 3484](https://www.ietf.org/rfc/rfc3484.txt)).
-
-For example, if there is container with the desired hostname on the local
-machine, the application receives that container's IP address.
-Otherwise, the application receives the IP address of a random
-container with the desired hostname.
-
 When weaveDNS is queried for a name in a domain other than
 `.weave.local`, it queries the host's configured nameserver, which is
 the standard behaviour for Docker containers.

site/weavedns/load-balance-fault-weavedns.md

@@ -33,6 +33,14 @@ PING pingme.weave.local (10.32.0.2) 56(84) bytes of data.
 
 Notice how the ping reaches different addresses.
 
+However, due to
+[RFC 3484 address selection](https://tools.ietf.org/html/rfc3484#section-6)
+most DNS resolver libraries prefer certain addresses over others, to
+the point where in some circumstances the same address is always
+chosen. To avoid this behaviour, applications may want to perform
+their own address selection, e.g. by choosing a random entry from the
+result of
+[`getaddrinfo()`](http://pubs.opengroup.org/onlinepubs/9699919799/functions/getaddrinfo.html).
 
 ## <a name="fault-resilience"></a>Fault Resilience