[Bug 1084771] Re: Gateway not added when in different subnet

[Grimeton]

I knew it...

Do me a favour - read RFC 2461 http://www.ietf.org/rfc/rfc2461.txt

===== SNIP ====== 8< ============================

    Unlike IPv4, the recipient of an IPv6 redirect assumes that the
      new next-hop is on-link.  In IPv4, a host ignores redirects
      specifying a next-hop that is not on-link according to the link's
      network mask.  The IPv6 redirect mechanism is analogous to the
      XRedirect facility specified in [SH-MEDIA].  It is expected to be
      useful on non-broadcast and shared media links in which it is
      undesirable or not possible for nodes to know all prefixes for
      on-link destinations.

====== >8 ========= SNAP ========================

...


** Changed in: ifupdown (Ubuntu)
       Status: Invalid => New

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https://bugs.launchpad.net/bugs/1084771

Title:
  Gateway not added when in different subnet

Status in “ifupdown” package in Ubuntu:
  New

Bug description:
  Hi,

  as with IPv6 it became usual to have gateways in different subnets
  than the subnet that is handed out. So it can happen that you get this
  subnet: "2a01:db8:1234::/64" and the gateway is "2a01:db8::1/128"
  which is in a different subnet.

  If one adds such a gateway to "/etc/network/interfaces" it is not
  added by the scripts, as there is no route to this host on the system.
  This is correct, but doesn't solve the problem.

  To solve it, it is necessary to add a "local" route to the gateway,
  like so:

  "ip -6 route add 2a01:db8::1" dev $interface".

  This lets the system send NDP requests for the gateway's MAC address
  and makes it able to add the default route like so:

  "ip -6 route add default via 2a01:db8::1".

  The same problem exists in IPv4, but it's not a common scenario to use
  a gateway in a different subnet there.

  And please, please, don't tell me a gateway has to be in the same
  subnet as the client...

  If you have any questions feel free to contact me.

  KR,

  Oliver

  ProblemType: Bug
  DistroRelease: Ubuntu 12.10
  Package: ifupdown 0.7.2ubuntu2
  ProcVersionSignature: Ubuntu 3.5.0-18.29-generic 3.5.7
  Uname: Linux 3.5.0-18-generic x86_64
  ApportVersion: 2.6.1-0ubuntu6
  Architecture: amd64
  Date: Thu Nov 29 23:43:58 2012
  MarkForUpload: True
  ProcEnviron:
   LANGUAGE=en_US:
   TERM=screen
   PATH=(custom, no user)
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  SourcePackage: ifupdown
  UpgradeStatus: No upgrade log present (probably fresh install)

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