improve comments. we don't usually need explicit configs.

src/etc/rtadvd.conf

@@ -1,19 +1,27 @@
-#	$OpenBSD: rtadvd.conf,v 1.1 1999/12/11 10:33:26 itojun Exp $
+#	$OpenBSD: rtadvd.conf,v 1.2 2000/03/17 17:18:59 itojun Exp $
 #	$NetBSD: rtadvd.conf,v 1.3 1999/07/03 20:50:39 hubertf Exp $
-#
+
 # common definitions.
-#
-default:\
-	:chlim#64:raflags#0:rltime#1800:rtime#30000:retrans#1000:\
-	:pinfoflags#192:vltime#3600000:pltime#3600000:mtu#1500:
-ether:\
-	:mtu#1500:tc=default:
-#
-# interfaces.
-#
-# This is a sample entry.  You'll need to have an entry like this
-# for each of your interfaces on which you'll be advertising about the prefix
-# information.
-# Then, list name of the interfaces to be advertised onto the command line.
+# Note: All of the following parameters have default values defined
+#       in specifications, and hence you usually do not have to set them
+#       by hand unless you need special non-default values.
+#       You even do not need to create the configuration file. rtadvd
+#       would usually work well without a configuration file.
+#       See also: rtadvd(8)
+
+#default:\
+#	:chlim#64:raflags#0:rltime#1800:rtime#30000:retrans#1000:\
+#	:pinfoflags#192:vltime#3600000:pltime#3600000:mtu#1500:
+#ether:\
+#	:mtu#1500:tc=default:
+
+# per-interface definitions.
+#   IPv6 prefixes are configured in this part. However, rtadvd
+#   automatically learns appropriate prefixes from the kernel's routing
+#   table and advertises the prefixes, so you don't have to configure
+#   this part, either.
+#   If you don't want the automatic advertisement, invoke rtadvd with
+#   the -s option and configure this part by hand.
+
 #ef0:\
-#	:addrs#1:addr="fec0:0000:0000:0000::":prefixlen#64:tc=ether:
+#	:addrs#1:addr="3ffe:0501:ffff:0000::":prefixlen#64:tc=ether: