Re: ping to internet hosts through NameServer of provider
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On Tuesday 09 March 2004 9:29 am, Stanislav Puffler DiS. wrote: > Hi all, > i´m newbie to fw, have just installed iptables and configured. Have 3 > interfaces, eth0 - internet, eth1 - DMZ (squid, postfix), eth2 - LAN. My > provider has connected my firewall to the Internet via 1 public IP (on > eth0). Internet hosts are resolved via provider´s Name Server (this IP > 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´t ping to internet hosts correctly (only on IP - it is > without need of contacting providers NS) - it is working like this : > > [user@machine]$ ping www.rb.cz > IN=eth0 OUT= MAC=.............. SRC="my_providers_nameserver_ip" > DST="ip_on_my_eth0" LEN=127 TOS=0x00 PREC=0x00 TTL=61 ID=3268 DF > PROTO=UDP SPT=53 DPT=32792 LEN=107 So you have a LOGging rule (presumably some time before a DROP rule - not many people LOG ACCEPTed packets), which shows that you are blocking DNS replies from your ISP. Hence you cannot resolve IP addresses. > Ping to resolved IP of www.rb.cz is no problem (ping 22.214.171.124 - > 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´s NS to resolv internet hosts ? Please tell us your ruleset (either the iptables commands you use to set up the rules, or the output of "iptables -L -nv; iptables -L -t nat -nv") and we can suggest what might be wrong. If you are new to networking as well as netfilter, please read one of the excellent tutorials accessible from http://www.netfilter.org and this will help you get a basic setup working. I can recommend Oskar Andreasson's tutorial at http://iptables-tutorial.frozentux.net Regards, Antony. -- Most people are aware that the Universe is big. - Paul Davies, Professor of Theoretical Physics Please reply to the list; please don't CC me.