Network settings fouled up

davidstvz · 06-14-2010, 01:45 PM

I've got a laptop that was recently being used in India, and now that the professor is back I need to reset the network connection to work with our system again. However, I'm having quite a bit of trouble. I've gotten it working manually (by editing the /etc/network/interfaces file, running ifup and then manually adding the gateway to the routing table using the route command), but it won't automatically start with the system.

Simply using the System tool for Network Connections has no effect.

After a fresh reboot, if I use route or netstat -nr there is an extra entry that normally isn't present on our other machines (169.254.0.0). I can't even find a file where that number is stored. It's not in /etc/networks or /etc/network/interfaces

Is there anyway to just erase the existing settings and start fresh?

EDIT

Well I just fixed it with an ugly hack (going into /etc/init.d/networking and adding 'ifup eth0' and 'route add default gw [my gateway ip]' just before the exit command, but I'd still like to get a better idea of what's going on if anyone has some info. Maybe I can do it the right way.

AlucardZero · 06-14-2010, 02:21 PM

You need to tell us what distro you are using. By the presence of /etc/network/interfaces, it's Debian-derived, but that's all we know.

Post the contents of /etc/network/interfaces. You probably want "auto eth0" instead of "iface eth0" or whatever your eth0 stanza starts with.

As for 169.254.0.0:

Quote:

Comment: This is the "link local" block. It was set
Comment: aside for this special use in the Standards
Comment: Track document, RFC 3927 and was further
Comment: documented in the Best Current Practice
Comment: RFC 5735, which can be found at:
Comment: http://www.rfc-editor.org/rfc/rfc3927.txt
Comment: http://www.rfc-editor.org/rfc/rfc5735.txt
Comment: It is allocated for communication between hosts
Comment: on a single link. Hosts obtain these addresses
Comment: by auto-configuration, such as when a DHCP
Comment: server cannot be found.
Comment: A router MUST NOT forward a packet with an IPv4
Comment: Link-Local source or destination address,
Comment: irrespective of the router's default route configuration
Comment: or routes obtained from dynamic routing protocols.
Comment: A router which receives a packet with an IPv4
Comment: Link-Local source or destination address MUST NOT
Comment: forward the packet. This prevents forwarding of
Comment: packets back onto the network segment from which
Comment: they originated, or to any other segment.

rweaver · 06-14-2010, 02:24 PM

Code:

"Autoconfiguration" IP Addresses:
        169.254.0.0 - 169.254.255.255
Addresses in the range 169.254.0.0 to 169.254.255.255 are used automatically by some PCs and Macs when they are configured to use IP, do not have a static IP Address assigned, and are unable to obtain an IP address using DHCP.

This traffic is intended to be confined to the local network, so the administrator of the local network should look for misconfigured hosts. Some ISPs inadvertently also permit this traffic, so you may also want to contact your ISP. This is documented in RFC 5735.

This isn't an error most times, it usually happens when it can't correctly dhcp an address. Check your settings to see what is running on startup...

What is in your interfaces file?

davidstvz · 06-15-2010, 09:37 AM

The distro is some version of Ubuntu (that's why I'm in the Ubuntu forum).

For the manual config, it may be as simple as changing iface to auto. I'll try it.

I'm still wondering where the GUI networking tool stores its info. I was swapping between two IPs (to make sure there wasn't a conflict) and the networking tool definitely isn't reading the /etc/network/interfaces file.