[Bug 1218442] Re: IPv6 addresses are lost when an interface is shortly down

[stcheng]

I think this is the kernel setting. Please check this:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/Documentation/networking
/ip-sysctl.txt?id=refs/tags/v4.6.1#n1571

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Title:
  IPv6 addresses are lost when an interface is shortly down

Status in ifupdown package in Ubuntu:
  Confirmed

Bug description:
  /etc/network/interfaces has been configured with IPv4 and IPv6
  addresses on an interface. There are two networks each:

  $ ip -4 addr show dev eth0
  2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
      inet 10.1.1.51/24 brd 10.1.1.255 scope global eth0
      inet 10.2.1.51/24 brd 10.2.1.255 scope global eth0

  $ ip -6 addr show dev eth0
  2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qlen 1000
      inet6 xxxx:yyyy:zzzz:201::33/64 scope global 
         valid_lft forever preferred_lft forever
      inet6 xxxx:yyyy:zzzz:101::33/64 scope global 
         valid_lft forever preferred_lft forever
      inet6 fe80::aaaa:aaff:febb:ccdd/64 scope link 
         valid_lft forever preferred_lft forever

  (Global addresses and MAC address anonymized)

  Both are configured within "manual" entries in
  /etc/network/interfaces.

  
  When I turn down eth0 and bring it up again, the result is:

  $ ip -4 addr show dev eth0
  2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
      inet 10.1.1.51/24 brd 10.1.1.255 scope global eth0
      inet 10.2.1.51/24 brd 10.2.1.255 scope global eth0

  $ ip -6 addr show dev eth0
  2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qlen 1000
      inet6 fe80::aaaa:aaff:febb:ccdd/64 scope link 
         valid_lft forever preferred_lft forever

  That is, the global IPv6 addresses are lost.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: ifupdown 0.7.5ubuntu2
  ProcVersionSignature: Ubuntu 3.8.0-29.42-generic 3.8.13.5
  Uname: Linux 3.8.0-29-generic x86_64
  ApportVersion: 2.9.2-0ubuntu8.3
  Architecture: amd64
  Date: Thu Aug 29 16:28:46 2013
  InstallationDate: Installed on 2013-08-14 (14 days ago)
  InstallationMedia: Kubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
  MarkForUpload: True
  SourcePackage: ifupdown
  UpgradeStatus: No upgrade log present (probably fresh install)

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