Add IPv6 address to existing IPv4 interface not working

Question

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:~$

Solution

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.

Comments

[xhienne]

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.

[rustyx]

You can also just specify netmask as a suffix in the address: address 192.168.1.2/24