Created attachment 65260 [details]
Fragment of /var/log/messages

This is the fragment of /var/log/messages from the insertion of the eth plug (sorry it's RJ45 not RJ11, isn't it? ;)

With a netmask of 255.255.255.0, your IP address (10.1.6.26) and your gateway (10.1.2.31) are not actually on the same subnet.  As far as IP is concerned, 10.1.2.31 is on a different network from your computer and therefore is not reachable.  It appears that your DHCP server may be giving out bad leases.

The first entry in your "good" routing table is a host entry which says the gateway is directly reachable through eth0.  That shouldn't be necessary -- normally the route for the local subnet (the second entry in your "good" routing table, and the only entry in the bad one) matches the gateway as well.

It's worth looking into what's generating that host route in the non-NetworkManaged case.  It might be some distribution-specific script hooked into the DHCP client, or it might be a route provided as part of the DHCP lease itself.  (If the latter, it would mean the DHCP server isn't actually giving out bad leases, but instead that NM is ignoring information provided in the lease.)  Either way it would be helpful in determining the nature of the problem.

I'm sorry it took me so long :)

I am not a network expert, but I must agree that the network config is somewhat strange... but it works with the default connection mechanism, so guess what the admin would tell me if asked to change this ;)

I narrowed down the precise place where this route is added in the Fedora script.
It is /sbin/dhclient which does this.

It is invoked in the script /etc/sysconfig/network-scripts/ifup-eth

I put some debug stuff in
the script and the following fragment of the script:

    echo DEBUG 850
    route -n
    for i in ${DHCLIENTARGS} ${DEVICE}; do if [ -f "$i" ]; then echo File $i; cat $i; else echo Option $i; fi; done
    set -x

    if /sbin/dhclient ${DHCLIENTARGS} ${DEVICE} ; then
        echo $" done."
    else
        echo $" failed."
        exit 1
    fi
  else
    ....
fi

echo DEBUG 900
route -n
  

prints out the content of the attachment ("Zrobione" means done in Polish :)

Jacek
PS. The script comes from this FC5 package: initscripts-8.31.1-1
/sbin/dhclient comes from dhclient-3.0.3-26

Created attachment 66526 [details]
Output of ifup-eth

Is this still a problem with 0.6 or 0.7?

I can't tell as the network layout at my faculty has changed (several times) since the bug was reported. Now the layout is standard, i.e., the gateway is on the local network. 

BTW: NetworkManager-0.7.0-0.11.svn4022.4.fc9.i386 works well for me now!

ok, thanks.