Network

Note

The IP addresses shown here, are documentation examples. You need to use your own addresses. See Router for network and IP configuration.

We have dual-Stack IPv4 and IPv6 on our internal network (LAN).

The IPv6 addresses are globally routed official internet addresses assigned to us by our IPv6 internet provider.

The IPv4 addresses are private network addresses.

The router supplies most of the relevant settings by autoconfiguration, and we like to keep it that way. The only exception are additional fixed IP addresses for hosted services.

Interface Configuration

Edit the /etc/network/interfaces.

Leave the ethernet interface at its default settings:

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0

# Autoconfigured IPv4 interface
iface eth0 inet dhcp

# Autoconfigured IPv6 interface
iface eth0 inet6 auto

Add additional static IPv4 and IPv6 addresses for each service and virtual host:

# Port-forwarded connections from firewall-router
iface eth0 inet static
    address 192.0.2.10/24
iface eth0 inet6 static
    address 2001:db8::10/64

# www.example.net
iface eth0 inet static
    address 192.0.2.11/24
iface eth0 inet6 static
    address 2001:db8::11/64

# cloud.example.net
iface eth0 inet static
    address 192.0.2.12/24
iface eth0 inet6 static
    address 2001:db8::12/64

# xmpp.example.net
iface eth0 inet static
    address 192.0.2.13/24
iface eth0 inet6 static
    address 2001:db8::13/64

# ns1.example.net
iface eth0 inet static
    address 192.0.2.14/24
iface eth0 inet6 static
    address 2001:db8::14/64

# bt.example.net
iface eth0 inet static
    address 192.0.2.15/24
iface eth0 inet6 static
    address 2001:db8::15/64

Add as many adresses as needed, as long as they are not already defined on other devices or assigned trough autoconfiguration. This gets easier if you reserve a range like 10 to 90 to this server and only assign addresses from that range.

For easier recognition and administration the last number of any IPv4 and IPv6 address is identical (e.g. 192.0.2.10 and 2001:db8::10).

Restart the network services with:

$ sudo service networking restart

Usefull Commands

Add new IP address

Here is how to add a new IP addresses on the fly, without restarting the service.

Note

If the newly addded address is not added in the /etc/network/interfaces it will be lost after system reboot.

Add IPv4 address:

$ sudo ip addr add 192.0.2.99/24 dev eth0

Add IPv6 address:

$ sudo ip addr add 2001:db8:26:845::99/64 dev eth0

Show IP addresses

To show all currently active IP addresses:

$ ip addr show

Network Restart

Altough there is a networking service, it can not be restarted. The usual command sudo service networking restart fails with a message like the following:

stop: Job failed while stopping
start: Job is already running: networking

This is intentional on Ubuntu servers since 14.04

Instead of the service, the interfaces have to be restarted:

sudo ifdown eth0 && sudo ifup eth0

Removing a IPv6 Route

sudo ip -6 route del ::/0 via fe80::2cb0:5dff:fe7f:2dba