61

I have used Ubuntu since Ubuntu 8.10; today I'm working with Ubuntu 12.04 Server.

I am having difficulty keeping static routes on booting. I would usually put the route commands 

/sbin/route add -net <IP>/<MASK> <GW> dev <ethX>

in /etc/rc.local or I would create a file (named routes) inside the directory /etc/network/if-up/, but I notice that on Ubuntu 12.04 it isn't working.

If I type the commands in the shell, they work, but the same commands don't work when they are in the specified file.

I already tried to change the file name to other names thinking that my file name (routes) could be erroneous in Ubuntu 12.04, but that also did not work.

I notice also that command /sbin/ifconfig works, less the /sbin/route.

What changed in network set-up?

How can I define static routes on Ubuntu 12.04?

Eric Carvalho
  • 55,453
Frank Allan
  • 611

8 Answers8

75

You can put static routes in /etc/network/interfaces:

auto eth0
iface eth0 inet static
      address 192.168.1.2
      netmask 255.255.255.0
      up route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1
      up route add -net 172.16.0.0 netmask 255.240.0.0 gw 192.168.1.1
Peter Turner
  • 616
Eric Carvalho
  • 55,453
20

I found very often that the correct place to define a static route is in /etc/network/interfaces, it is ok if you are going to globally restart the network with /etc/init.d/networking restart for example. But if you are going to use ifdown and ifup to individually shutdown an interface, ifup will end with the error:

ifup eth1

RTNETLINK answers: File exists
Failed to bring up eth1.

Because of it tries to define a route but it is already defined. The interface will be up anyway but, ifup will not update /run/network/ifstate so next time you will us ifdown you will not able to do it unless you use the --force flag.

To make ifup to continue configuring even if routes are already defined, you can use this format when defining routes in /etc/network/interfaces

up ip route add 172.16.0.0/24 via 192.168.10.1 || true
up ip route add 192.168.0.0/16 via 192.168.10.1 || true

This way you will have the warning in the output but the interface configuration will be completed

ifup eth1

RTNETLINK answers: File exists
RTNETLINK answers: File exists
ssh stop/waiting
ssh start/running, process 18553
Eric Carvalho
  • 55,453
mseisdedos
  • 201
13

As it is 2021 you can config it using netplan on ubuntu 18.04 or later (tested on ubuntu 20.04). compelete reference is available on netplan site. the config file can be found under /etc/netplan/ directory.

network:
  version: 2
  ethernets:
    ens160: # in my case the interface name is ens160
      dhcp4: false  # or true. depends on your situation
      addresses: [192.168.0.10/24]  # your static IP address
      # the actual answer is here
      routes:
        - to: 0.0.0.0/0  # or any other subnet you like. 0.0.0.0/0 means default gateway
          via: 172.16.0.1  # or any other gateway you want.
          on-link: true   # as you see my interface IP address and default gateway are not in the same subnet so we should put this true but if they are in the same subnet this is not required.

PS. the YAML configuration files are sensitive to indentation and it does not accept tabs. the indentation is 2 spaces.

don't forget run netplan apply.

Iman Kermani
  • 231
9

You can try this (add it to /etc/network/interfaces), this is almost complete way for setting routes:

auto eth0
iface eth0 inet static
    post-up /sbin/route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1
    post-up /bin/mount -t nfs 192.168.0.203:/motd/ /motd/
Eliah Kagan
  • 119,640
mmehboobhan
  • 91
6

There is a package ifupdown-extra avaible in Ubuntu.
It provides automatic scripts (installed in /etc/network/*/), one of which is used to add static routes.

The configuration file for this is /etc/network/routes

The top of this config file has a good description:

This configuration file is read by the static-routes if-updown script and the /etc/init.d/networking-routes script to setup a list of routes associated either with a given interface or global routes.

An example route I use is:

192.168.240.0 255.255.255.0 192.168.130.3 em3
NGRhodes
  • 9,680
4

Using nmcli I was able to run a persistent solution (@isapir solution didn't work on my device).

sudo nmcli connection modify <conection-name> +ipv4.routes "<ip>/<mask> <gw> <mt>"

For example:

sudo nmcli connection modify ssid-name +ipv4.routes "1.1.1.0/24 192.168.0.1 100"

After that applying the changes is possible by setting the connection down and up again (no need for full NetworkManager restart):

sudo nmcli con down ssid-name ; sudo nmcli con up ssid-name

To see current connections run:

sudo nmcli connection
ofirule
  • 553
3

I prefer to use nmcli.

nmcli device modify <device> +ipv4.routes "<ip>/<mask> <gw>" ipv4.route-metric 0

For example:

nmcli device modify wlp2s0 +ipv4.routes "1.1.1.0/24 192.168.0.1" ipv4.route-metric 0

After that apply the changes by restarting the NetworkManager service:

sudo systemctl restart NetworkManager.service
isapir
  • 591
3

what worked for us was

sudo route add -net 192.168.0.2/32 gw 192.168.1.1 netmask 255.255.0.0

i used to run on a Mac:

sudo route -n add -net 192.168.0.2/32 192.168.1.1

but on a ubuntu the "gw" between IPs and the last "netmask" part was missing (also -n not required on ubuntu)

Peter Perháč
  • 359