Debian up in /etc/network/interfaces not working

Question

I'm trying to add a secondary IPv6 address to eth0 on Debian Sid.

I added the following lines to /etc/network/interfaces:

iface eth0 inet6 static
  address [IPv6 address #1]
  netmask 64
  gateway [IPv6 gateway]
  pre-up echo 0 > /proc/sys/net/ipv6/conf/eth0/autoconf
  up /sbin/ifconfig eth0 inet6 add [IPv6 address #2]/64

After a reboot there is only one IPv6 address assigned to eth0. However, if I simply execute the command (/sbin/ifconfig eth0 inet6 add [IPv6 address #2]/64) manually, I have 2 IPv6 addresses assigned to eth0, just like I want.

It looks like the up command is just not executed at all. Has this been changed? I do have a /etc/network/if-up.d directory, but I read that those scripts may be run more than once.

How can I make up work or add a second IPv6 address on Debian Sid?

Solution

Not a direct answer to why up doesn't work, but maybe a solution for your problem:

I usually use the same configuration style for multiple IPv4 and IPv6 addresses for consistency. This is the configuration of one of my servers:

auto eth0
iface eth0 inet static
    address 94.142.242.211
    netmask 28
    gateway 94.142.242.209

iface eth0 inet6 static
    address 2a02:898:148::211
    netmask 64
    gateway 2a02:898:148::1

auto eth0:0
iface eth0:0 inet static
    address 94.142.242.212
    netmask 28

iface eth0:0 inet6 static
    address 2a02:898:148::212
    netmask 64

auto eth0:1
iface eth0:1 inet static
    address 94.142.242.217
    netmask 28

iface eth0:1 inet6 static
    address 2a02:898:148::217
    netmask 64

The IPv6 addresses show up on eth0 not on eth0:0 and eth0:1 when seen through ifconfig:

eth0      Link encap:Ethernet  HWaddr 00:50:56:80:96:82  
          inet addr:94.142.242.211  Bcast:94.142.242.223  Mask:255.255.255.240
          inet6 addr: 2a02:898:148::217/64 Scope:Global
          inet6 addr: 2a02:898:148::212/64 Scope:Global
          inet6 addr: 2a02:898:148::211/64 Scope:Global
          inet6 addr: fe80::250:56ff:fe80:9682/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0:0    Link encap:Ethernet  HWaddr 00:50:56:80:96:82  
          inet addr:94.142.242.212  Bcast:94.142.242.223  Mask:255.255.255.240
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0:1    Link encap:Ethernet  HWaddr 00:50:56:80:96:82  
          inet addr:94.142.242.217  Bcast:94.142.242.223  Mask:255.255.255.240
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

I don't know why your configuration doesn't work, but maybe doing it this way will work for you...

Comments

[kasperd]

Try putting a touch command in the file instead of the ifconfig command, that way you can verify if the command gets executed at all. Also verify if it makes a difference whether DAD is enabled or disabled.

[Louis Matthijssen]

Thanks, I changed it to up touch /root/ipv6test but the file doesn't exist after a reboot.

[kasperd]

Does up work if you put in an inet stanza rather than an inet6 stanza?

[kasperd]

According to the documentation I am looking at up and post-up are synonyms. May still be worth testing if using one or the other makes a difference.

[Louis Matthijssen]

Thanks, it seems to work but then I can't ping anything. Example (ping6 google.com): 11 packets transmitted, 0 received, 100% packet loss, time 10080ms. Removing the lines makes it work again.

[Sander Steffann]

The Linux kernel usually chooses the last added IPv6 address as its default source address. For IPv4 it will use the address on eth0 and not those on eth0:*. So in the config above it would probably use 94.142.242.211 and 2a02:898:148::217 by default. Maybe your firewall settings need to be adjusted for that.

[Sander Steffann]

PS: The default source address can be overridden manually by executing i.e. /sbin/ip -6 route add default via 2a02:898:148::1 src 2a02:898:148::211 metric 1.

[Louis Matthijssen]

If I add the address manually I can ping using both IP addresses (ping6 -I [IPv6 address #1] google.com and ping6 -I [IPv6 address #2] google.com both work). So I guess it's not a firewall issue? I've never had this problem before.

[Sander Steffann]

That is weird indeed... No idea how that can happen. Can you show the output of ip -6 addr and ip -6 route after adding the lines in /etc/network/interfaces?

[Louis Matthijssen]

Okay I just saw that IPv6 sometimes just stops working. This answer is working for me! I'll contact my ISP about the weird IPv6 availability.

[Sander Steffann]

Feel free to contact me off-list to tell me which ISP it is, I know many of them so maybe I can help :)