add a CAVEATS section documenting some issues when using roundrobin

and loadbalance protocols;

brad, claudio, and sthen all helped explain this to me,
and sthen helped me put the diff together;

1 files changed, 13 insertions, 2 deletions

diff --git a/share/man/man4/trunk.4 b/share/man/man4/trunk.4
index 395981809ba..699d5789d25 100644
--- a/share/man/man4/trunk.4
+++ b/share/man/man4/trunk.4
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: trunk.4,v 1.20 2007/10/22 14:48:52 pyr Exp $
+.\"	$OpenBSD: trunk.4,v 1.21 2008/01/06 13:41:45 jmc Exp $
 .\"
 .\" Copyright (c) 2005, 2006 Reyk Floeter <reyk@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: October 22 2007 $
+.Dd $Mdocdate: January 6 2008 $
 .Dt TRUNK 4
 .Os
 .Sh NAME
@@ -122,3 +122,14 @@ The
 .Nm
 driver was written by
 .An Reyk Floeter Aq reyk@openbsd.org .
+.Sh CAVEATS
+The trunk protocols
+.Ic roundrobin
+and
+.Ic loadbalance
+require a switch which supports IEEE 802.3ad link aggregation
+for multicast/broadcast packets.
+Otherwise protocols which cannot properly deal with duplicate packets,
+such as
+.Xr inet6 4
+duplicate address detection (DAD), will not work.