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Reviewed:  https://review.openstack.org/233287
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=b6126bc0f17f348ff6303b9bd6041cb018479ef9
Submitter: Jenkins
Branch:    master

commit b6126bc0f17f348ff6303b9bd6041cb018479ef9
Author: Sreekumar S <sreesiv@xxxxxxxxx>
Date:   Sat Oct 10 03:18:00 2015 +0530

    Fix for adding gateway with IP outside subnet
    
    Currently 'force_gateway_on_subnet' configuration is set to True
    by default and enforces the subnet on to the gateway. With this
    fix 'force_gateway_on_subnet' can be changed to False, and
    gateway outside the subnet can be added.
    Before adding the default route, a route to the gateway IP is
    added. This applies to both external and internal networks.
    
    This configuration option is deprecated, and should be removed
    in a future release. It should always allow gateway outside the
    subnet. This is done as a separate patch
    https://review.openstack.org/#/c/277303/
    
    Change-Id: I3a942cf98d263681802729cf09527f06c80fab2b
    Closes-Bug: #1335023
    Closes-Bug: #1398768


** Changed in: neutron
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1335023

Title:
  Neutron fails to create external network gateway when gateway's IP in
  different subnet with br-ex

Status in neutron:
  Fix Released

Bug description:
  Hi guys,

  I encountered a problem with neutron when trying to create external
  network with gateway in different subnet:

  neutron subnet-create ext-net --name ext-subnet \
    --allocation-pool start=46.105.252.216,end=46.105.252.219\
    --disable-dhcp --gateway 176.31.105.254 46.105.252.0/24

  The external network has gateway in different subnet: 46.105.252.216/24 and 176.31.105.254
  I need something like this due to the router configuration in DC.

  The problem is neutron show no error, and on dashboard, the ext-net
  also shows its gateway 176.31.105.254. However, packets are not routed
  because in IP routing table of the router, no default gateway entry is
  added:

  sudo ip netns exec qrouter-f918cbb7-dc0c-4713-a6f5-3c66b46e12cf route
  -n

  Destination     Gateway         Genmask         Flags Metric Ref
  Use Iface

  46.105.252.0    0.0.0.0         255.255.255.0   U     0      0        0 qg-0103d6fa-31
  192.168.100.0   0.0.0.0         255.255.255.0   U     0      0        0 qr-343ab2cb-f5

  I can work around by manually adding two line in routing table:

  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  0.0.0.0         176.31.105.254  0.0.0.0         UG    0      0        0 qg-0103d6fa-31
  46.105.252.0    0.0.0.0         255.255.255.0   U     0      0        0 qg-0103d6fa-31
  176.31.105.254  0.0.0.0         255.255.255.255 UH    0      0        0 qg-0103d6fa-31
  192.168.100.0   0.0.0.0         255.255.255.0   U     0      0        0 qr-343ab2cb-f5

  Then it worked fine!
  I believe this is a bug, due to adding gateway with different subnet in routing table will be rejected. In this case, we need to add this line first before adding gateway:

  176.31.105.254  0.0.0.0         255.255.255.255 UH    0      0
  0 qg-0103d6fa-31

  So either we need to show users an error "not allow to add gateway in
  different subnet", or we should support adding gateway properly.

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