3

Probably a simple answer but I can't seem to find it. I am running a multihomed Debian Stable(latest) and on interface eth1 I need both IPv4 and IPv6 address. My /etc/network/interfaces looks like this:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

auto eth0
allow-hotplug eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet static
        address 192.168.1.2
        netmask 255.255.255.0
        gateway 192.168.1.1
        up ip -6 address add 2001:470:28:5b2::1/64 dev $IFACE

The problem is the interface only gets assigned the IPv4 adress, not the IPv6 address. What am I missing?

When running ifup -av:

g00nz@debie:~$ sudo ifup -av
[sudo] password for g00nz:
run-parts --exit-on-error --verbose /etc/network/if-pre-up.d
run-parts: executing /etc/network/if-pre-up.d/wpasupplicant
Configuring interface eth1=eth1 (inet)
run-parts --exit-on-error --verbose /etc/network/if-pre-up.d
run-parts: executing /etc/network/if-pre-up.d/wpasupplicant
ip addr add 192.168.1.2/255.255.255.0 broadcast 192.168.1.255     dev eth1 label eth1
RTNETLINK answers: File exists
Failed to bring up eth1.
run-parts --exit-on-error --verbose /etc/network/if-up.d
run-parts: executing /etc/network/if-up.d/avahi-daemon
run-parts: executing /etc/network/if-up.d/mountnfs
run-parts: executing /etc/network/if-up.d/openssh-server
run-parts: executing /etc/network/if-up.d/upstart
run-parts: executing /etc/network/if-up.d/wpasupplicant

It seems that eth1 is already configured and I can't add the IPv6 address but when I do it from bashprompt it works:

sudo ip -6 addr add 2001:470:28:5b2::1/64 dev eth1

and check with ifconfig eth1:

g00nz@debie:~$ sudo ip -6 addr add 2001:470:28:5b2::1/64 dev eth1
g00nz@debie:~$ sudo ifconfig eth1
eth1      Link encap:Ethernet  HWaddr 00:24:9b:08:4b:aa
          inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: 2001:470:28:5b2::1/64 Scope:Global
          inet6 addr: fe80::224:9bff:fe08:4baa/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:4254 errors:0 dropped:2080 overruns:0 frame:0
          TX packets:305 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:469773 (458.7 KiB)  TX bytes:45395 (44.3 KiB)

Anyone? :(

/roger

OK, tried this and got this in my /etc/network/interfaces now:

auto eth1
iface eth1 inet static
        address 192.168.1.2
        netmask 255.255.255.0
        gateway 192.168.1.1

iface eth1 inet6 static
        address 2001:470:28:5b2::1
        netmask 64

But still, when I check with ip a I have:

3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:24:9b:08:4b:aa brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.2/24 brd 192.168.1.255 scope global eth1
       valid_lft forever preferred_lft forever
    inet6 fe80::224:9bff:fe08:4baa/64 scope link
       valid_lft forever preferred_lft forever

I does not stick :(

Still get error with ifup:

g00nz@debie:~$ sudo ifup -av
[sudo] password for g00nz:
run-parts --exit-on-error --verbose /etc/network/if-pre-up.d
run-parts: executing /etc/network/if-pre-up.d/wpasupplicant
Configuring interface eth1=eth1 (inet)
run-parts --exit-on-error --verbose /etc/network/if-pre-up.d
run-parts: executing /etc/network/if-pre-up.d/wpasupplicant
ip addr add 192.168.1.2/255.255.255.0 broadcast 192.168.1.255     dev eth1     label eth1
RTNETLINK answers: File exists
Failed to bring up eth1.
run-parts --exit-on-error --verbose /etc/network/if-up.d
run-parts: executing /etc/network/if-up.d/avahi-daemon
run-parts: executing /etc/network/if-up.d/mountnfs
run-parts: executing /etc/network/if-up.d/openssh-server
run-parts: executing /etc/network/if-up.d/upstart
run-parts: executing /etc/network/if-up.d/wpasupplicant
g00nz@debie:~$
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1
  • 1
    Can you add a down line, with the opposite ip -6 addr del command, force an ifdown and see if an ifup works better? Or retry your ifup after removing manually your ipv6 addr if ip -6 addr del. Forcing an ifdown is better. Commented Jan 14, 2017 at 12:45

2 Answers 2

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14

Your ifup probably doesn't run because the interface already has the IPv4 address and it can't add it twice. It will not even reach the IPv6 line. If you can you should bring the interface down so all addresses are removed, and then bring it up again.

Configuring IPv6 should be done in a different way though:

auto eth1
iface eth1 inet static
    address 192.168.1.2
    netmask 255.255.255.0
    gateway 192.168.1.1

iface eth1 inet6 static
    address 2001:470:28:5b2::1
    netmask 64

You can also add a gateway if you want.

PS: many people don't seem to know, but you can also use netmask 24 for IPv4. You don't have to spell out netmask 255.255.255.0.

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  • 5
    You can also just specify netmask as a suffix in the address: address 192.168.1.2/24 Commented Oct 13, 2018 at 10:17
0

I just hit this issue in 2025

It seems to be caused by an oddity of how ifreload works on systems with networking.service (but not on systems using ifupdown2).

The fix is simple remove the gateway on the second interface from both the IPv4 and IPv6 lines

so for example

this doesn't work

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
allow-hotplug eth0
iface eth0 inet static
  address 192.168.1.41
  netmask 255.255.255.0
  gateway 192.168.1.1
  dns-nameservers 192.168.1.5  192.168.1.6

iface eth0 inet6 static
  accept_ra = 2
  address redacted:1::41
  netmask 64
  gateway redacted:1::1
  dns-nameservers redacted:1::5 redacted:1::6


# This is a manuall configured interface fro the ceph mesh
auto eth1
allow-hotplug eth1
iface eth1 inet static
  address 10.0.81.41
  netmask 255.255.255.0
  gateway 10.0.81.1
  up ip route add 10.0.0.80/28 via 10.0.81.1 dev eth1

iface eth1 inet6 static
  address fc00:81::41
  netmask 64
  gateway fc00:81::1
  up ip -6 route add fc00::80/124 via fc00:81::1 dev eth1

but this does work! - weird um 'feature'

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
allow-hotplug eth0
iface eth0 inet static
  address 192.168.1.41
  netmask 255.255.255.0
  gateway 192.168.1.1
  dns-nameservers 192.168.1.5  192.168.1.6

iface eth0 inet6 static
  accept_ra = 2
  address redacted:1::41
  netmask 64
  gateway redacted:1::1

  dns-nameservers redacted:1::5 redacted:1::6


# This is a manuall configured interface fro the ceph mesh
auto eth1
allow-hotplug eth1
iface eth1 inet static
  address 10.0.81.41
  netmask 255.255.255.0
#  gateway 10.0.81.1
  up ip route add 10.0.0.80/28 via 10.0.81.1 dev eth1

iface eth1 inet6 static
  address fc00:81::41
  netmask 64
#  gateway fc00:81::1
  up ip -6 route add fc00::80/124 via fc00:81::1 dev eth1
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  • Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center. Commented Apr 30 at 3:50

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