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[Launchpad Bug Tracker <1980178@xxxxxxxxxxxxxxxxxx>]

[Expired for neutron because there has been no activity for 60 days.]

** Changed in: neutron
       Status: Incomplete => Expired

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https://bugs.launchpad.net/bugs/1980178

Title:
  Metadata becomes unreachable after adding more than 21 subnets to same
  network

Status in neutron:
  Expired

Bug description:
  Problem description :

  Neutron adds separate entries for each network to dnsmasq's "dhcp-
  optsfile".

  Metadata becomes unreachable after adding more than 21 subnets to same
  network.

  Due to DHCP limitations, it's not possible to distribute more than 23 routes within classless-static-route (option 121).
  One route is necessarily needed for default gateway and one route is needed for the metadata service.
  So, adding more than 21 routes breaks the option 121 and creating new instance with metadata is failing.

  Also, adding more than 21 subnets to the same network crashes running
  Windows instances NIC's.

  Windows instances which got leases from DHCP, after the lease time request for lease renewal.
  Windows Server 2008, Windows Server 2012 and Windows Server 2016 operating systems becomes unreachable after that renewal request.
  Disabling and enabling the NIC helps to get instance to communicate with the network.
  I believe it discards the option 121 which is broken, it only gets IP address, subnet mask and gateway informations but not route table.

  Release -- Wallaby

  Build Used
  neutron-common                         2:18.3.0-0ubuntu1~cloud0
  neutron-dhcp-agent                     2:18.3.0-0ubuntu1~cloud0
  neutron-l3-agent                       2:18.3.0-0ubuntu1~cloud0
  neutron-linuxbridge-agent              2:18.3.0-0ubuntu1~cloud0
  neutron-metadata-agent                 2:18.3.0-0ubuntu1~cloud0
  neutron-plugin-ml2                     2:18.3.0-0ubuntu1~cloud0
  neutron-server                         2:18.3.0-0ubuntu1~cloud0
  python3-neutron                        2:18.3.0-0ubuntu1~cloud0
  python3-neutron-lib                    2.10.1-0ubuntu1~cloud0
  python3-neutronclient                  1:7.2.1-0ubuntu1~cloud0

  Steps Performed

  1. Created a network with a couple of subnets first.

  2. Added more than 30 subnets into that network.
  3. Tried to provision new instances with metadata.

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