RTNETLINK answers: File exists on Linux. What it meant?

I run command dhclient eth1 and it always said:

RTNETLINK answers: File exists

How can I solve this problem?

It means you need to remove eth1 as gateway or route as you are trying to add a new rule that conflicts with an existing route rule. The syntax is as follows to flush or delete

sudo ip addr flush dev {networkDeviceNameHere}
sudo ip addr flush dev eth1

Verify route with ip command:

ip route

Now run:

sudo dhclient eth1

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