From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jim Laurino Subject: Re: dhcrelay still responds dropped inbound offer packets from iptables (nfcan: addressed to exclusive sender for this address) Date: Fri, 8 Jul 2005 17:37:49 -0400 Message-ID: <20050708213749.GC17745@salty> References: <673fb82305070814186036ce2f@mail.gmail.com> Reply-To: nfcan.x.jimlaur@dfgh.net Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <673fb82305070814186036ce2f@mail.gmail.com> (from +nfcan+jimlaur+7a8d75f853.changwilly#gmail.com@spamgourmet.com on Fri, Jul 08, 2005 at 17:18:33 -0400) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: netfilter-bounces@lists.netfilter.org Errors-To: netfilter-bounces@lists.netfilter.org Content-Type: text/plain; format="Flowed"; delsp="Yes"; charset="us-ascii" To: netfilter@lists.netfilter.org On 2005.07.08 17:18, Willy Chang - changwilly@gmail.com wrote: > Folks, > > I am running a dhrelay service and using iptables to be a > firewall to block packets from dhcp server on the inbound side, eth0, > of my Liunx. The reason to do this is to avoid generating duplicated > packets from my machine to dhcp client on the same subnet. > For some reasons, I am unable to block these packets. I have a > simple rule setting below to simply block all incoming UDP packets > where it should block dhcp package as well. > > iptables -A INPUT -p UDP -i eth0 -j DROP I see two things to comment on. First, if you add (-A) a rule like this at the end, the packets in question might have already been accepted by an earlier rule. For a case like this, you might want to insert at the top (-I) instead. Second, INPUT affects filtering of packets bound for the firewall host itself. FORWARD rules affect packets bound for other hosts. I think those are the packets you are trying to block. -- Jim Laurino nfcan.x.jimlaur@dfgh.net Please reply to the list. Only mail from the listserver reaches this address.