The following patch is adopted from ISC DHCP version 4.3.0.

http://ftp.isc.org/isc/dhcp/4.3.0/dhcp-4.3.0.tar.gz

--- dhcp-4.1-ESV-R7/server/stables.c.orig	Thu Aug 23 19:23:54 2012

+++ dhcp-4.1-ESV-R7/server/stables.c	Mon Apr 28 16:37:14 2014

@@ -244,6 +244,7 @@

 	{ "delayed-ack", "S",			&server_universe,  58, 1 },

 	{ "max-ack-delay", "L",			&server_universe,  59, 1 },

 #endif

+	{ "ignore-client-uids", "f",		&server_universe,  60, 1 },

 	{ NULL, NULL, NULL, 0, 0 }

 };

--- dhcp-4.1-ESV-R7/server/dhcp.c.orig	Thu Aug 23 19:23:54 2012

+++ dhcp-4.1-ESV-R7/server/dhcp.c	Mon Apr 28 16:36:18 2014

@@ -2304,31 +2304,40 @@

 	/* Update Client Last Transaction Time. */

 	lt->cltt = cur_time;

-	/* Record the uid, if given... */

-	oc = lookup_option (&dhcp_universe, packet -> options,

-			    DHO_DHCP_CLIENT_IDENTIFIER);

-	if (oc &&

-	    evaluate_option_cache (&d1, packet, lease,

-				   (struct client_state *)0,

-				   packet -> options, state -> options,

-				   &lease -> scope, oc, MDL)) {

-		if (d1.len <= sizeof lt -> uid_buf) {

-			memcpy (lt -> uid_buf, d1.data, d1.len);

-			lt -> uid = lt -> uid_buf;

-			lt -> uid_max = sizeof lt -> uid_buf;

-			lt -> uid_len = d1.len;

-		} else {

-			unsigned char *tuid;

-			lt -> uid_max = d1.len;

-			lt -> uid_len = d1.len;

-			tuid = (unsigned char *)dmalloc (lt -> uid_max, MDL);

-			/* XXX inelegant */

-			if (!tuid)

-				log_fatal ("no memory for large uid.");

-			memcpy (tuid, d1.data, lt -> uid_len);

-			lt -> uid = tuid;

+	/* See if we want to record the uid for this client */

+	oc = lookup_option(&server_universe, state->options,

+	    SV_IGNORE_CLIENT_UIDS);

+	if ((oc == NULL) ||

+	    !evaluate_boolean_option_cache(&ignorep, packet, lease, NULL,

+		packet->options, state->options,

+		&lease->scope, oc, MDL)) {

+

+		/* Record the uid, if given... */

+		oc = lookup_option (&dhcp_universe, packet -> options,

+		    DHO_DHCP_CLIENT_IDENTIFIER);

+		if (oc &&

+		    evaluate_option_cache (&d1, packet, lease,

+			(struct client_state *)0,

+			packet -> options, state -> options,

+			&lease -> scope, oc, MDL)) {

+			if (d1.len <= sizeof lt -> uid_buf) {

+				memcpy (lt -> uid_buf, d1.data, d1.len);

+				lt -> uid = lt -> uid_buf;

+				lt -> uid_max = sizeof lt -> uid_buf;

+				lt -> uid_len = d1.len;

+			} else {

+				unsigned char *tuid;

+				lt -> uid_max = d1.len;

+				lt -> uid_len = d1.len;

+				tuid = (unsigned char *)dmalloc (lt -> uid_max, MDL);

+				/* XXX inelegant */

+				if (!tuid)

+					log_fatal ("no memory for large uid.");

+				memcpy (tuid, d1.data, lt -> uid_len);

+				lt -> uid = tuid;

+			}

+			data_string_forget (&d1, MDL);

 		}

-		data_string_forget (&d1, MDL);

 	}

 	if (host) {

--- dhcp-4.1-ESV-R7/server/dhcpd.conf.5.orig	Wed May  7 18:37:36 2014

+++ dhcp-4.1-ESV-R7/server/dhcpd.conf.5	Wed May  7 18:38:46 2014

@@ -2302,6 +2302,19 @@

 must be a constant value.

 .RE

 .PP

+The

+.I ignore-client-uids

+statement

+.RS 0.25i

+.PP

+.B ignore-client-uids \fIflag\fB;\fR

+.PP

+If the \fIignore-client-uids\fR statement is present and has a value of

+\fItrue\fR or \fIon\fR, the UID for clients will not be recorded.

+If this statement is not present or has a value of \fIfalse\fR or

+\fIoff\fR, then client UIDs will be recorded.

+.RE

+.PP

 The

 .I infinite-is-reserved

 statement

--- dhcp-4.1-ESV-R7/includes/dhcpd.h.orig	Thu Aug 23 19:23:53 2012

+++ dhcp-4.1-ESV-R7/includes/dhcpd.h	Mon Apr 28 16:11:17 2014

@@ -627,6 +627,7 @@

 #define SV_LIMIT_PREFS_PER_IA		57

 #define SV_DELAYED_ACK			58

 #define SV_MAX_ACK_DELAY		59

+#define SV_IGNORE_CLIENT_UIDS		60

 #if !defined (DEFAULT_PING_TIMEOUT)

 # define DEFAULT_PING_TIMEOUT 1