macro.ntpbrd

sharewall is very good

#
# Shorewall version 4 - NTPbrd Macro
#
# /usr/share/shorewall/macro.NTPbrd
#
#	This macro handles NTP traffic (ntpd) including replies to Broadcast
#	NTP traffic.
#
#	It is recommended only to use this where the source host is trusted -
#	otherwise it opens up a large hole in your firewall because
#	Netfilter doesn't track connections for broadcast traffic.
#
###############################################################################
#ACTION	SOURCE	DEST	PROTO	DEST	SOURCE	RATE	USER/
#				PORT(S)	PORT(S)	LIMIT	GROUP
PARAM	-		-		udp	123
PARAM	-		-		udp	1024:	123
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE