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Create a persistent static route

Specific to

Debian-based distributions

Tested on

Debian (Etch, Lenny, Squeeze)
Ubuntu (Hardy, Intrepid, Jaunty, Karmic, Lucid, Maverick, Natty, Precise, Trusty)


To create a persistent static route to a remote network via a gateway.


Suppose that a host is connected via eth0 to the subnet with the address The default gateway for this subnet is, but to reach the subnet it is necessary to use a different gateway at


Ideally the route should be added immediately after the relevant interface has been brought up, and removed immediately before it is taken down. This can be achieved using up and down commands in /etc/network/interfaces.

First ensure that the relevant interface is down (if it is not already):

ifdown eth0

Next add suitable up and down commands to the relevant interface definition within the interfaces file. If an interface definition does not already exist then you will need to add one:

auto eth0
iface eth0 inet static
  up /sbin/route add -net netmask gw
  down /sbin/route del -net netmask

If there is more than one route to be created then this can be done using multiple up and down commands.

Once the interfaces file has been modified, bring the interface back up:

ifup eth0


Print the routing table using the route command:

route -n

When the interface is up you should be able to see the new route (the line with a destination of

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface   U     0      0        0 eth0       UG    0      0        0 eth0         UG    0      0        0 eth0

If you take the interface down again then all three of these routes should disappear.


Network is unreachable

If ifup gives an error of the form:

SIOCADDRT: Network is unreachable
Failed to bring up eth0.

then the likely cause is that the specified gateway is not directly reachable via any local interface. Gateways must be reachable in a single hop: having a route to them is not sufficient.

No such process

In place of ‘Network is unreachable’, recent versions of the Kernel may return the rather less helpful message:

SIOCDELRT: No such process
Failed to bring up eth0.

File exists

An error of the form:

SIOCADDRT: File exists
Failed to bring up eth0.

indicates that there is already a route to the specified destination via the specified gateway. One way this could happen is by bringing the interface up manually (using ifconfig and route) and then attempting to bring it up using ifup. If you suspect that something like this has happened then you should manually restore the interface and routing table (using ifconfig and route) to the state expected by ifup and ifdown.

Tags: routing