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

[Phillip Susi]

It is not possible to use a gateway on a different subnet.  By
definition, being on a different subnet means the gateway is not
reachable on this network.


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

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Title:
  Gateway not added when in different subnet

Status in “ifupdown” package in Ubuntu:
  Invalid

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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