Neil, Doesn't look like my original message made it to the mailing list so here you are. ---------- Forwarded Message ---------- Subject: Re: Fwd: [CentOS] HOW to enable traceroute with IPTABLES Date: Sat February 17 2007 10:07 From: Robert Spangler <lazydog at zoominternet.net> To: CentOS mailing list <centos at centos.org> On Sat February 17 2007 03:11, Indunil Jayasooriya wrote: > > I am setting up a firewall on CENTOS 4.4. > > > > > > I have enabled ICMP to www.google.com > > > > iptables -A OUTPUT -p icmp -d 64.233.189.104 -j ACCEPT > > iptables -A INPUT -p icmp -s 64.233.189.104 -j ACCEPT > > traceroute uses by default UDP with port 33434. While this is true for a starting point, this is not the whole story. Traceroute starts on this port but every time it sends out a packet the port number is increased automatically. Why? Simple, the TTL is exceeded so traceroute sends out on the next port in numerical order. Thus traceroute needs more then 33434 open there should be a range of ports open. Traceroute does not always start on this port either I have found out. Sometimes it starts on a hight port but only by a few hopes. > I wrote below 2 rules > > iptables -A OUTPUT -p udp -d 64.233.189.104 --dport 33434 -j ACCEPT > iptables -A INPUT -p udp -s 64.233.189.104 --sport 33434 -j ACCEPT I have the following ( I do not restrict traceroute destination); -A OUTPUT -o eth0 -p udp --dport 33200:33500 -m state --state NEW -j ACCEPT Also you don't need the INPUT statement if you have ESTABLISHED,RELATED at the top of your INPUT chain. > Then I tried as below [snip] > But Still the same. > > WHY? I placing my money on the port settings > IF my rules are wrong can you rectify it ? See above. -- Regards Robert Smile... it increases your face value! ------------------------------------------------------- -- Regards Robert Smile... it increases your face value!