Hi everyone! The problem is solved. It turns out that I forgot to install the DNS server on my first computer and there is actually NOTHING wrong in the firewall settings of the entire network.
First, I successfully pinged some IP addresses (151.189.21.100, which is www.arcor.online.net) from the internet from Computer B (the one sharing the internet from Computer A). Then I opened up Firefox in Computer B and typed the IP address and it also worked. However when I typed the URL "http://www.arcor-online.net", then Firefox failed to fetch the site. Therefore this pointed to the domain name resolving problem, which resolved after I used the ADSL modem as my DNS server address for Computer B. Dominik On 6/11/05, Dominik Margraf <[EMAIL PROTECTED]> wrote: > On 6/11/05, Roberto C. Sanchez <[EMAIL PROTECTED]> wrote: > > On Sat, Jun 11, 2005 at 08:25:14PM +1200, Dominik Margraf wrote: > > > > > > I also installed ipmasq on computer A. Computer A was able to access > > > the internet. Both Computer A and B could also ping each other > > > successfully and computer B was also able to share internet from > > > computer A > > > > > What is the output of '/sbin/route -n' from each computer? > > for Computer A (the one connected to the ADSL modem): > > [EMAIL PROTECTED]:~$ /sbin/route -n > Kernel IP routing table > Destination Gateway Genmask Flags Metric Ref Use Iface > 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 > 10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth1 > 0.0.0.0 10.1.1.1 0.0.0.0 UG 0 0 0 eth1 > [EMAIL PROTECTED]:~$ > > (note: eth1 is the port connected to the ADSL modem and eth0 is the > port connected to Computer B via a crossover cable) > > for Computer B: > [EMAIL PROTECTED]:~$ /sbin/route -n > Kernel IP routing table > Destination Gateway Genmask Flags Metric Ref Use Iface > 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 > 0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 > eth0 > [EMAIL PROTECTED]:~$ > > > > > > However after I reinstalled Computer A with the newly released debian > > > 3.1r0a (with exactly the same settings described above) with ipmasq, > > Uh. Why did you reinstall? > > > > > Because I would like to reallocate the disc space and set up a new > partition for storing my DVD files. > > > > > computer B could not obtain internet access any more despite computer > > > A still had internet access and computer B was also able to share CUPS > > > and NFS services from computer A successfully. Also, computer B was > > > able to ping computer A and vice versa. > > > > > > So what could go wrong here? Is it because some problems with the > > > firewall and/or ipmasq? How could I fix this problem? > > What firewall program/configuration are you using? What is the output > > if 'iptables -nL' ? > > > > -Roberto > > > I did not intentionally install firewall program for both computer or > tweak the firewall configurations. I just installed the ipmasq > package, which allows NAT by recomputing the firewall rules. However > there are the printouts for "iptablees -nL" of both computers: > > > Computer A: > > debian1:/home/abc# iptables -nL > Chain INPUT (policy DROP) > target prot opt source destination > ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 > LOG all -- 127.0.0.0/8 0.0.0.0/0 LOG flags > 0 level 4 > DROP all -- 127.0.0.0/8 0.0.0.0/0 > ACCEPT all -- 0.0.0.0/0 255.255.255.255 > ACCEPT all -- 192.168.0.0/24 0.0.0.0/0 > ACCEPT !tcp -- 0.0.0.0/0 224.0.0.0/4 > LOG all -- 192.168.0.0/24 0.0.0.0/0 LOG flags > 0 level 4 > DROP all -- 192.168.0.0/24 0.0.0.0/0 > ACCEPT all -- 0.0.0.0/0 255.255.255.255 > ACCEPT all -- 0.0.0.0/0 10.1.1.5 > ACCEPT all -- 0.0.0.0/0 10.255.255.255 > LOG all -- 0.0.0.0/0 0.0.0.0/0 LOG flags > 0 level 4 > DROP all -- 0.0.0.0/0 0.0.0.0/0 > > Chain FORWARD (policy DROP) > target prot opt source destination > ACCEPT all -- 192.168.0.0/24 0.0.0.0/0 > ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state > RELATED,ESTAB LISHED > LOG all -- 0.0.0.0/0 192.168.0.0/24 LOG flags > 0 level 4 > DROP all -- 0.0.0.0/0 192.168.0.0/24 > LOG all -- 0.0.0.0/0 0.0.0.0/0 LOG flags > 0 level 4 > DROP all -- 0.0.0.0/0 0.0.0.0/0 > > Chain OUTPUT (policy DROP) > target prot opt source destination > ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 > ACCEPT all -- 0.0.0.0/0 255.255.255.255 > ACCEPT all -- 0.0.0.0/0 192.168.0.0/24 > ACCEPT !tcp -- 0.0.0.0/0 224.0.0.0/4 > LOG all -- 0.0.0.0/0 192.168.0.0/24 LOG flags > 0 level 4 > DROP all -- 0.0.0.0/0 192.168.0.0/24 > ACCEPT all -- 0.0.0.0/0 255.255.255.255 > ACCEPT all -- 10.1.1.5 0.0.0.0/0 > ACCEPT all -- 10.255.255.255 0.0.0.0/0 > LOG all -- 0.0.0.0/0 0.0.0.0/0 LOG flags > 0 level 4 > DROP all -- 0.0.0.0/0 0.0.0.0/0 > debian1:/home/abc# > > > Computer B: > > debian2:/home/abc# iptables -nL > Chain INPUT (policy ACCEPT) > target prot opt source destination > > Chain FORWARD (policy ACCEPT) > target prot opt source destination > > Chain OUTPUT (policy ACCEPT) > target prot opt source destination > debian2:/home/abc# > > Thank you very much for your help and I would be grateful if you could > find the culprit! > > Dominik >