dhclient: What does "RTNETLINK answers: File exists" Mean?
Solution 1:
Basically what happens is that dhclient adds a route to the routing table.
It tries this while the route is already in the table.
Check
ip route
for a route which was added by the dhcp server.
For having the lease renewed do
dhclient -r
if thats not enough you can remove all leases by removing the file and getting a new lease
sudo rm /var/lib/dhcp/dhclient.leases; sudo dhclient eth0
Depending on your exact setup this might be an issue with having to type your password twice, so watch out for that.