Problem with default gateway
 

network interface eth1 is receiving addressing via dhcp. it was originally assigned a static address in a different network. current network is 172.16.4.0/24 but previous network was 192.168.88.0/24. DHCP settings are correct, as I have numerous devices learning address/default gateway info. For some reason the old gateway 192.168.88.1 is stuck as default gateway, even with new dhcp assignment. removal via "ip route del" does not work and says "RTNETLINK answers: Operation not permitted" sudo is not installed. advice? The install is Debian 8 and it hasn't been updated. Also manual editing via the GUI does not seem to have any effect.

I'm assuming that you're not using NetworkManager here, but instead manual network configuration has been employed. If so, check the configuration in /etc/network/interfaces, specifically any gateway setting that may still be present.

Reference:
https://wiki.debian.org/NetworkConfi...rface_manually

To clarify this detail:
To edit the routing table, you must have root privileges. If you can’t use sudo, log on as root or use the su command. In both cases, you will be asked for the root password (although you can configure authentication so that su doesn’t require the password).

If you are trying to make system changes as a normal user, you have missed a very basic part of how Linux operates as a multiuser system. Most any system type changes require root/admin privileges as suggested above so you either use root to make these changes or install sudo. I don't use Debian regularly but my most recent experience using it is on the install DVD, it used sudo but with the actual installation it was necessary to create a root user/password. If you know the root password, your problem is solved.

Thank you. I knew I needed root, I just couldn't figure out how to get there. I had to manually edit the routing table and I'm not sure why. Nothing showed up in /etc/network/interfaces and it persisted through reboot. I'm not sure why it is remembering the old static assignment.

Then you need to tell us which network management framework you're using - Wicd, NetworkManager...?