[NTLUG:Discuss] Network problems

[Keith Rice]

James Corona wrote:
> 
> I'm having trouble getting a RedHat 5.1 server to talk on my network.  I
> have a 5.2 server running without a problem and have tried to compare
> configurations; there is nothing obviously different.  I can ping both
> directions server - client  client - server but when I try to get an IP
> number through DHCP.  Using the debugger I can see the server receives the
> request but when it responds it gives an error that says Network
> Unavailable.  In addition I am using diald to automatically connect to my
> ISP.  When a request is sent from the client the connection is activated but
> no data is ever recieved.  This is making me crazy,  where else might I
> look?
> 
> Thank
> 
> James

I experienced a problem with dhcpd with RH 5.1 which sounds like yours. I had to
make sure that the default route on the server (the RH 5.1 box) was set to my
ethernet card (route add default eth0) and then it worked fine except when I
went online because my default route was set to my ppp connection. I had to
tweak my ppp-off script to switch the default route back to eth0 after I
disconnected. When the ppp-on script called pppd it specified that the default
route was to be set to the ppp link. When I reloaded my system with Mandrake 5.2
the problem went away. I assume the problem is with the version of dhcpd and not
RedHat 5.1 but I never tried to upgrade my dhcpd to find out. I suggest that you
upgrade to the latest dhcpd and see if that helps. Otherwise, if you don't want
to try the upgrade you can try tweaking the ppp scripts to do the default route
switching.

About your problem of not receiving data once diald activates your connection.
It looks like it may be one of a couple of things. It could be that you don't
have a routing table entry for your local net. Try adding a static route for
your local net. My LAN uses private Class C addressing. My subnet is
192.168.0.0. Here's my /etc/sysconfig/network-scripts/ifcfg-eth0 file:

DEVICE=eth0
IPADDR=192.168.0.1
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
ONBOOT=yes

This way, even if you are online, all packets from your server sent to systems
on your LAN are sent out the correct interface.

If this doesn't work, you may not have IP forwarding enabled on your server. You
can enable it by changing your FORWARD_IPV4 setting in /etc/sysconfig/network to
true. Also, be sure to setup IP masquerading using ipfwadm. See the Linux IP
Masqurade mini HOWTO for help on this step.

I hope this helps you out.

Keith

-- 
Keith Rice           E-Mail..: dkrcomp at earthlink.net
Hurst, Texas, USA    WWW.....: http://home.earthlink.net/~dkrcomp
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