problem solved (was Re: failing to share internet access between two PCs installed with Debian 3.1)

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• In reply to: Dominik Margraf: "Re: failing to share internet access between two PCs installed with Debian 3.1"
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Date: Sun, 12 Jun 2005 21:42:11 +1200
To: "Roberto C. Sanchez" <roberto@familiasanchez.net>, debian-user@lists.debian.org

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 <dominik.margraf@gmail.com> wrote:
> On 6/11/05, Roberto C. Sanchez <roberto@familiasanchez.net> 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):
>
> abc@debian1:~$ /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
> abc@debian1:~$
>
> (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:
> abc@debian2:~$ /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
> abc@debian2:~$
>
> >
> > > 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
>

• Previous message: Matthias Luckhardt: "transcode with pp filter crashes on Sarge (works on Sid)"
• In reply to: Dominik Margraf: "Re: failing to share internet access between two PCs installed with Debian 3.1"
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