I was getting this error on a MFEL, but it is applicable to any Linux server with multiple NICs.

I‘m typing the following command under Ubuntu Linux:

  route add default gw 192.168.3.2 eth0

But it is giving me out the following error:

  SIOCADDRT: File exists

How do I fix this problem?

This error normally displayed when you try to modify or or add a new routing IP address. For example, when you set the same route multiple times you will get this error.

Understanding SIOCADDRT: File exists Message

1. 1.SIOC: Serial Input Output Controller.
2. 2.ADD: ADD (addition).
3. 3.RT: RouTe (routing ip).
4. 4.File exists – Routing is already configured so delete wrong one and add the new one.

Open a command-line terminal (select Applications > Accessories > Terminal), and then type the following command to see your current routing table:

  netstat -r
  
  or
  
  ip route list

Use the following syntax:

  sudo ip route delete {IP/SUBNET} dev {INTERFACE}

To delete default route 192.168.1.0/24 via eth0, enter:

  sudo ip route delete 192.168.1.0/24 dev eth0

Type the following command:

  sudo ip route add default via 192.168.3.2
  
  OR
  
  sudo route add default gw 192.168.3.2 eth0

Edit, /etc/network/interfaces file and setup the correct routing address:

  auto eth0
      iface eth0 inet static
       address 192.168.3.10
       network 192.168.3.0
       netmask 255.255.255.0
       broadcast 192.168.3.255
       ### set router default ip here ###
       gateway 192.168.3.2

Originally from http://www.cyberciti.biz/faq/siocaddrt-file-exists-ubuntu-linux-error-solution/