diff -Nrux .svn -x work /usr/ports/net/isc-dhcp41-server/Makefile isc-dhcp41-server/Makefile
--- /usr/ports/net/isc-dhcp41-server/Makefile	2011-04-10 14:40:52.000000000 -0700
+++ isc-dhcp41-server/Makefile	2011-05-07 17:02:56.874671113 -0700
@@ -31,8 +31,10 @@
 
 UNIQUENAME=	${PKGNAMEPREFIX}${PORTNAME}${PKGNAMESUFFIX}
 
+OPTIONS=	DHCP_IPV6 "Enable support for IPv6" on
+
 .if ${SUBSYS} == server
-OPTIONS=	DHCP_PARANOIA "Enable support for chroot" on \
+OPTIONS+=	DHCP_PARANOIA "Enable support for chroot" on \
 		DHCP_LDAP "Experimental LDAP backend support" off \
 		DHCP_LDAP_SSL "Support LDAP connection over SSL/TLS" on
 .endif
@@ -72,7 +74,10 @@
 MAN1=		omshell.1
 MAN3=		dhcpctl.3 omapi.3
 CFLAGS+=	-fPIC
-CONF_FILE=	dhcpd.conf dhcpd6.conf
+CONF_FILE=	dhcpd.conf
+.if defined(WITH_DHCP_IPV6)
+CONF_FILE+=	dhcpd6.conf
+.endif
 .else
 MAN8+=		dhcrelay.8
 .endif
@@ -135,6 +140,14 @@
 SUB_LIST+=	PARANOIA=no
 .endif
 
+.if defined(WITH_DHCP_IPV6)
+CONFIGURE_ARGS+=	--enable-dhcpv6
+PLIST_SUB+=		IPV6=""
+.else
+CONFIGURE_ARGS+=	--disable-dhcpv6
+PLIST_SUB+=		IPV6="@comment "
+.endif
+
 pre-patch:
 .if ${SUBSYS} == server && defined(WITH_DHCP_LDAP)
 	@cd ${WRKSRC} && ${PATCH} -p1 < ${WRKDIR}/${LDAPPATCHDIST}/${LDAPPATCHFILE}
@@ -155,9 +168,11 @@
 	${MAKE} -C ${WRKSRC}/includes install
 	${MAKE} -C ${WRKSRC}/common install
 	${INSTALL_DATA} ${WRKSRC}/dhcpctl/dhcpctl.h ${PREFIX}/include
+.if defined(WITH_DHCP_IPV6)
 	${INSTALL_DATA} ${WRKSRC}/doc/examples/dhcpd-dhcpv6.conf \
 		${PREFIX}/etc/dhcpd6.conf.sample
 .endif
+.endif
 .if defined(WITH_DHCP_LDAP)
 	@${MKDIR} ${SCHEMA_DIR}
 	${INSTALL_DATA} ${LDAP_SCHEMA} ${SCHEMA_DIR}
@@ -180,8 +195,10 @@
 .if ${SUBSYS} == client
 	${INSTALL_SCRIPT} ${WRKSRC}/client/scripts/freebsd ${PREFIX}/sbin/dhclient-script
 .elif ${SUBSYS} == server
+.if defined(WITH_DHCP_IPV6)
 	@${LN} -sf isc-dhcpd ${PREFIX}/etc/rc.d/isc-dhcpd6
 .endif
+.endif
 	@${SED} ${PKGMESSAGE_SUB:S/$/!g/:S/^/ -e s!%%/:S/=/%%!/} \
 		${MSG_FILE} > ${PKGMESSAGE}
 .if defined(WITH_DHCP_LDAP)
diff -Nrux .svn -x work /usr/ports/net/isc-dhcp41-server/pkg-plist isc-dhcp41-server/pkg-plist
--- /usr/ports/net/isc-dhcp41-server/pkg-plist	2011-02-13 18:21:27.000000000 -0800
+++ isc-dhcp41-server/pkg-plist	2011-05-07 16:31:34.089931339 -0700
@@ -1,13 +1,13 @@
 @comment $FreeBSD: ports/net/isc-dhcp41-server/pkg-plist,v 1.4 2011/02/14 02:21:27 wxs Exp $
 @unexec %D/etc/rc.d/isc-dhcpd forcestop 2>/dev/null || true
-@unexec %D/etc/rc.d/isc-dhcpd6 forcestop 2>/dev/null || true
+%%IPV6%%@unexec %D/etc/rc.d/isc-dhcpd6 forcestop 2>/dev/null || true
 @unexec if cmp -s %D/etc/dhcpd.conf.sample %D/etc/dhcpd.conf; then rm -f %D/etc/dhcpd.conf; fi
 etc/dhcpd.conf.sample
 @exec if [ ! -f %D/etc/dhcpd.conf ] ; then cp -p %D/%F %B/dhcpd.conf; fi
-@unexec if cmp -s %D/etc/dhcpd6.conf.sample %D/etc/dhcpd6.conf; then rm -f %D/etc/dhcpd6.conf; fi
-etc/dhcpd6.conf.sample
-@exec if [ ! -f %D/etc/dhcpd6.conf ] ; then cp -p %D/%F %B/dhcpd6.conf; fi
-etc/rc.d/isc-dhcpd6
+%%IPV6%%@unexec if cmp -s %D/etc/dhcpd6.conf.sample %D/etc/dhcpd6.conf; then rm -f %D/etc/dhcpd6.conf; fi
+%%IPV6%%etc/dhcpd6.conf.sample
+%%IPV6%%@exec if [ ! -f %D/etc/dhcpd6.conf ] ; then cp -p %D/%F %B/dhcpd6.conf; fi
+%%IPV6%%etc/rc.d/isc-dhcpd6
 sbin/dhcpd
 bin/omshell
 %%LDAP%%bin/dhcpd-conf-to-ldap