From mboxrd@z Thu Jan 1 00:00:00 1970 From: Antony Stone Subject: Re: ping to internet hosts through NameServer of provider Date: Tue, 9 Mar 2004 10:40:28 +0000 Sender: netfilter-admin@lists.netfilter.org Message-ID: <200403091040.28256.Antony@Soft-Solutions.co.uk> References: <404D8E6C.2070107@seznam.cz> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <404D8E6C.2070107@seznam.cz> Errors-To: netfilter-admin@lists.netfilter.org List-Help: List-Post: List-Subscribe: , List-Id: List-Unsubscribe: , List-Archive: Content-Type: text/plain; charset="iso-8859-1" To: netfilter@lists.netfilter.org On Tuesday 09 March 2004 9:29 am, Stanislav Puffler DiS. wrote: > Hi all, > i=B4m newbie to fw, have just installed iptables and configured. Have 3 > interfaces, eth0 - internet, eth1 - DMZ (squid, postfix), eth2 - LAN. M= y > provider has connected my firewall to the Internet via 1 public IP (on > eth0). Internet hosts are resolved via provider=B4s Name Server (this I= P > is in /etc/resolv.conf). If I tried ping to (for example) www.rb.cz > before installing iptables, there was no problem. Now, after installing > iptables, I can=B4t ping to internet hosts correctly (only on IP - it i= s > without need of contacting providers NS) - it is working like this : > > [user@machine]$ ping www.rb.cz > IN=3Deth0 OUT=3D MAC=3D.............. SRC=3D"my_providers_nameserver_ip= " > DST=3D"ip_on_my_eth0" LEN=3D127 TOS=3D0x00 PREC=3D0x00 TTL=3D61 ID=3D32= 68 DF > PROTO=3DUDP SPT=3D53 DPT=3D32792 LEN=3D107 So you have a LOGging rule (presumably some time before a DROP rule - not= many=20 people LOG ACCEPTed packets), which shows that you are blocking DNS repli= es=20 from your ISP. Hence you cannot resolve IP addresses. > Ping to resolved IP of www.rb.cz is no problem (ping 193.86.103.40 - > returns a normal replay). Could anyone help me please how to set up > carefully and secure rule to maintain this problem - to permit my > provider=B4s NS to resolv internet hosts ? Please tell us your ruleset (either the iptables commands you use to set = up=20 the rules, or the output of "iptables -L -nv; iptables -L -t nat -nv") an= d we=20 can suggest what might be wrong. If you are new to networking as well as netfilter, please read one of the= =20 excellent tutorials accessible from http://www.netfilter.org and this wil= l=20 help you get a basic setup working. I can recommend Oskar Andreasson's=20 tutorial at http://iptables-tutorial.frozentux.net Regards, Antony. --=20 Most people are aware that the Universe is big. - Paul Davies, Professor of Theoretical Physics Please reply to the = list; please don't C= C me.