[K12OSN] server not forwarding packets for Windows clients

[R. Scott Belford]

Les Mikesell wrote:
> On Mon, 2006-01-30 at 14:54, Petre Scheie wrote:
>>> But I thought this should be enabled in a default k12ltsp install.
>>>
>> I think it is.  I built the server in my basement and successfully tested it with some 
>> thin clients; but I didn't try any Windows clients.  But I think something else must be 
>> going on because when I logged in at the console, while I could ping things like google 
>> & yahoo, firefox had trouble with them: first it wouldn't load any thing, then after 
>> shutting it down and restarting it, it could bring up a google page, but not yahoo; shut 
>> it down and restart it again and google and yahoo are accessible, but not others.  I ran 
>> 'host' on those & other websites and while I'd get an answer, I also got an error about 
>> the parser  receiving misformatted data.  In /etc/resolv.conf, there were two resolver 
>> addresses: the Linksys router, and the DNS server of the ISP.  I commented out the 
>> Linksys address, and then 'host' didn't get any more errors, but users still couldn't 
>> connect to the internet.  Here's how the network is layed out; it doesn't look like 
>> anything special to me.
>>
>> Internet-->ActionTec DSL bridge-->LinkSys Router w/wireless--> \
>>
>> -->8-port switch-->K12ltsp-->24-port switch-->clients
>>
>> I suppose I could check for bad packets and cables.  Any other ideas of things to look for?
> 
> Try to separate the DNS issues from packet forwarding/NAT.  The
> entries in /etc/resolv.conf are for DNS client lookups happening
> on the server itself.   The server also runs a DNS server that
> is used by the machines 'behind' it - that is, the ones that
> obtain their settings via DHCP.  You should be able to do
> a 'dig @localhost' on the server to see if the dns server
> is working and an 'nslookup some_internet_address' on a windows
> box behind it if so.  If that is OK, then move on to the
> nat/forwarding.   On the server:
> iptables --list -t nat
> should show
> Chain POSTROUTING (policy ACCEPT)
> target     prot opt source               destination
> MASQUERADE  all  --  anywhere             anywhere
> 

I believe that you will need to do this

echo 1 >> /proc/sys/net/ipv4/ip_forward

Then, edit your /etc/sysctl.conf and set the ip_forwarding variable to 1 
so that it is enabled upon next reboot.

--scott