Network access OK but server cannot use internet

Network access OK but server cannot use internet

Post by George Hewit » Mon, 04 Aug 2003 00:51:45



Ok hoping someone can help me, I have little hair left after this one...

I have a home network set up with a Redhat 8 box and 3 client PCs. The
redhat box has eth0 connected to the cable modem for Internet and eth1 as
the LAN which goes to a hub.

I have IP tables setup for NAT with Masquerading and forwards are accepted
from eth1. Inputs are also always accepted from eth1. Output policy is
ACCEPT, except for netbios stuff on eth0 which is dropped.

The problem is that client machines can use the internet no problem through
the server, but the server can not use the internet itself?!? Pages and
things keep timing out etc. Cannot ping using name or IP. My mailserver
(external) on the box can receive mail but cannot send at all (DNS
failiure). My ISP doesn't block any of this stuff, I know that for a fact.

Any ideas??

--

 
 
 

Network access OK but server cannot use internet

Post by Ian Northeas » Mon, 04 Aug 2003 02:27:04



> Ok hoping someone can help me, I have little hair left after this one...

> I have a home network set up with a Redhat 8 box and 3 client PCs. The
> redhat box has eth0 connected to the cable modem for Internet and eth1 as
> the LAN which goes to a hub.

> I have IP tables setup for NAT with Masquerading and forwards are accepted
> from eth1. Inputs are also always accepted from eth1. Output policy is
> ACCEPT, except for netbios stuff on eth0 which is dropped.

> The problem is that client machines can use the internet no problem through
> the server, but the server can not use the internet itself?!?

Have you omitted the state matching rule to allow responses back in the
*input* chain? E.g.:

iptables -A INPUT -i $EXTIF -m state --state ESTABLISHED,RELATED -j
ACCEPT

Regards, Ian

 
 
 

Network access OK but server cannot use internet

Post by George Hewit » Mon, 04 Aug 2003 03:05:09


Ha! That did it, thanks a million!

--



> > Ok hoping someone can help me, I have little hair left after this one...

> > I have a home network set up with a Redhat 8 box and 3 client PCs. The
> > redhat box has eth0 connected to the cable modem for Internet and eth1
as
> > the LAN which goes to a hub.

> > I have IP tables setup for NAT with Masquerading and forwards are
accepted
> > from eth1. Inputs are also always accepted from eth1. Output policy is
> > ACCEPT, except for netbios stuff on eth0 which is dropped.

> > The problem is that client machines can use the internet no problem
through
> > the server, but the server can not use the internet itself?!?

> Have you omitted the state matching rule to allow responses back in the
> *input* chain? E.g.:

> iptables -A INPUT -i $EXTIF -m state --state ESTABLISHED,RELATED -j
> ACCEPT

> Regards, Ian

 
 
 

1. cannot access mail server, rest of net OK

I just obtained a second email address from my ISP, Mindspring. I can't
reach that email server (pop.mindspring.com) and cannot figure out why.
Everything else seems to work fine. I can reach mail.mindspring.com, but
not pop.mindspring.com. nslookup indicates thay are the same IP address. I
can get mail by putting the IP address in the email client, but not when
using the hostname.

I can't ping pop.mindspring.com or traceroute to it.

I CAN access the host under Windows, however.

My DNS setup seems to be OK, as I said, everything else is OK.

I've talked with Mindspring tech support. They said if I were using
windows they'd have me re-install tcp/ip.

Any suggestions? I'm stumped.

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