add config note about cached community strings

Netdisco/lib/App/Netdisco/Manual/Configuration.pod

@@ -575,7 +575,7 @@ configuration.
 For SNMPv1 and SNMPv2, only the C<community> key is required.  Unlike the
 global C<community>/C<community_rw> setting, this is not a list but a single
 item. To emulate their list behaviour, have multiple entries at the top
-C<snmp_auth> level, as in the example above.
+C<snmp_auth> level, as in the example below.
 
 You can add C<read> and/or C<write> restrictions, and an IP restriction using
 C<only>. Giving the stanza a C<tag> name is optional, but recommended.
@@ -596,7 +596,7 @@ key to a stanza to override this.
 
 Note that multiple SNMP v2 community strings need to be in separate named
 stanza, as below. However for simple v2 configurations you can use the
-C<community> shorthand:
+C<community> shorthand instead:
 
  snmp_auth:
    - tag: 'default_v2_readonly1'
@@ -607,6 +607,11 @@ C<community> shorthand:
  # or...
  community: ['read1', 'read2']
 
+Netdisco caches both the successful SNMPv2 read and write community strings,
+as well as the C<tag> names if available. This allows for faster operations
+once a connection has already been made to a device. When you delete a device,
+the community strings are removed but the C<tag> hints remain, for future use.
+
 =head3 C<get_community>
 
 Value: String. Default none.