Document link-selection.

1 files changed, 15 insertions, 1 deletions

diff --git a/common/dhcp-options.5 b/common/dhcp-options.5
index 76d8448e..35a668ec 100644
--- a/common/dhcp-options.5
+++ b/common/dhcp-options.5
@@ -1,4 +1,4 @@
-.\"	$Id: dhcp-options.5,v 1.31 2006/07/26 15:43:52 shane Exp $
+.\"	$Id: dhcp-options.5,v 1.32 2007/04/18 15:53:14 dhankins Exp $
 .\"
 .\" Copyright (c) 2004-2006 by Internet Systems Consortium, Inc. ("ISC")
 .\" Copyright (c) 1996-2003 by Internet Software Consortium
@@ -1136,6 +1136,20 @@ So far, only bit zero (being the least significant bit) is defined in
 RFC3256.  If this bit is set to one, the host is considered a CPE
 Controlled Cable Modem (CCCM).  All other bits are reserved.
 .RE
+.PP
+.B option \fBagent.link-selection\fR \fIip-address\fR\fB;\fR
+.RS 0.25i
+.PP
+The link-selection suboption is provided by relay agents to inform servers
+what subnet the client is actually attached to.  This is useful in those
+cases where the giaddr (where responses must be sent to the relay agent)
+is not on the same subnet as the client.  When this option is present in
+a packet from a relay agent, the DHCP server will use its contents to find
+a subnet declared in configuration, and from here take one step further
+backwards to any shared-network the subnet may be defined within...the
+client may be given any address within that shared network, as normally
+appropriate.
+.RE
 .SH THE CLIENT FQDN SUBOPTIONS
 The Client FQDN option, currently defined in the Internet Draft
 draft-ietf-dhc-fqdn-option-00.txt is not a standard yet, but is in