503 lines
25 KiB
ReStructuredText
503 lines
25 KiB
ReStructuredText
.. _config-dhcp-ha:
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==========================
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High-availability for DHCP
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==========================
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This section describes how to use the agent management (alias agent) and
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scheduler (alias agent_scheduler) extensions for DHCP agents
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scalability and HA.
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.. note::
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Use the :command:`openstack extension list` command to check if these
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extensions are enabled. Check ``agent`` and ``agent_scheduler``
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are included in the output.
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.. code-block:: console
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$ openstack extension list --network -c Name -c Alias
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+-------------------------------------------------------------+---------------------------+
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| Name | Alias |
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+-------------------------------------------------------------+---------------------------+
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| Default Subnetpools | default-subnetpools |
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| Network IP Availability | network-ip-availability |
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| Network Availability Zone | network_availability_zone |
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| Auto Allocated Topology Services | auto-allocated-topology |
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| Neutron L3 Configurable external gateway mode | ext-gw-mode |
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| Port Binding | binding |
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| Neutron Metering | metering |
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| agent | agent |
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| Subnet Allocation | subnet_allocation |
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| L3 Agent Scheduler | l3_agent_scheduler |
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| Neutron external network | external-net |
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| Neutron Service Flavors | flavors |
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| Network MTU | net-mtu |
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| Availability Zone | availability_zone |
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| Quota management support | quotas |
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| HA Router extension | l3-ha |
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| Provider Network | provider |
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| Multi Provider Network | multi-provider |
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| Address scope | address-scope |
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| Neutron Extra Route | extraroute |
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| Subnet service types | subnet-service-types |
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| Resource timestamps | standard-attr-timestamp |
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| Neutron Service Type Management | service-type |
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| Router Flavor Extension | l3-flavors |
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| Neutron Extra DHCP opts | extra_dhcp_opt |
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| Resource revision numbers | standard-attr-revisions |
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| Pagination support | pagination |
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| Sorting support | sorting |
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| security-group | security-group |
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| DHCP Agent Scheduler | dhcp_agent_scheduler |
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| Router Availability Zone | router_availability_zone |
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| RBAC Policies | rbac-policies |
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| standard-attr-description | standard-attr-description |
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| Neutron L3 Router | router |
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| Allowed Address Pairs | allowed-address-pairs |
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| project_id field enabled | project-id |
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| Distributed Virtual Router | dvr |
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+-------------------------------------------------------------+---------------------------+
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Demo setup
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~~~~~~~~~~
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.. figure:: figures/demo_multiple_dhcp_agents.png
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There will be three hosts in the setup.
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.. list-table::
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:widths: 25 50
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:header-rows: 1
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* - Host
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- Description
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* - OpenStack controller host - controlnode
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- Runs the Networking, Identity, and Compute services that are required
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to deploy VMs. The node must have at least one network interface that
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is connected to the Management Network. Note that ``nova-network`` should
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not be running because it is replaced by Neutron.
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* - HostA
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- Runs ``nova-compute``, the Neutron L2 agent and DHCP agent
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* - HostB
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- Same as HostA
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Configuration
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~~~~~~~~~~~~~
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**controlnode: neutron server**
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#. Neutron configuration file ``/etc/neutron/neutron.conf``:
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.. code-block:: ini
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[DEFAULT]
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core_plugin = linuxbridge
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rabbit_host = controlnode
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allow_overlapping_ips = True
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host = controlnode
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agent_down_time = 5
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dhcp_agents_per_network = 1
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.. note::
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In the above configuration, we use ``dhcp_agents_per_network = 1``
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for this demonstration. In usual deployments, we suggest setting
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``dhcp_agents_per_network`` to more than one to match the number of
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DHCP agents in your deployment.
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See :ref:`conf-dhcp-agents-per-network`.
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#. Update the plug-in configuration file
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``/etc/neutron/plugins/linuxbridge/linuxbridge_conf.ini``:
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.. code-block:: ini
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[vlans]
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tenant_network_type = vlan
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network_vlan_ranges = physnet1:1000:2999
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[database]
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connection = mysql+pymysql://root:root@127.0.0.1:3306/neutron_linux_bridge
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retry_interval = 2
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[linux_bridge]
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physical_interface_mappings = physnet1:eth0
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**HostA and HostB: L2 agent**
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#. Neutron configuration file ``/etc/neutron/neutron.conf``:
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.. code-block:: ini
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[DEFAULT]
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rabbit_host = controlnode
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rabbit_password = openstack
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# host = HostB on hostb
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host = HostA
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#. Update the plug-in configuration file
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``/etc/neutron/plugins/linuxbridge/linuxbridge_conf.ini``:
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.. code-block:: ini
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[vlans]
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tenant_network_type = vlan
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network_vlan_ranges = physnet1:1000:2999
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[database]
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connection = mysql://root:root@127.0.0.1:3306/neutron_linux_bridge
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retry_interval = 2
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[linux_bridge]
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physical_interface_mappings = physnet1:eth0
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#. Update the nova configuration file ``/etc/nova/nova.conf``:
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.. code-block:: ini
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[DEFAULT]
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use_neutron=True
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firewall_driver=nova.virt.firewall.NoopFirewallDriver
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[neutron]
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admin_username=neutron
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admin_password=servicepassword
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admin_auth_url=http://controlnode:35357/v2.0/
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auth_strategy=keystone
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admin_tenant_name=servicetenant
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url=http://203.0.113.10:9696/
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**HostA and HostB: DHCP agent**
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- Update the DHCP configuration file ``/etc/neutron/dhcp_agent.ini``:
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.. code-block:: ini
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[DEFAULT]
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interface_driver = neutron.agent.linux.interface.BridgeInterfaceDriver
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Prerequisites for demonstration
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Admin role is required to use the agent management and scheduler extensions.
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Ensure you run the following commands under a project with an admin role.
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To experiment, you need VMs and a neutron network:
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.. code-block:: console
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$ openstack server list
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+--------------------------------------+-----------+--------+----------------+--------+----------+
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| ID | Name | Status | Networks | Image | Flavor |
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+--------------------------------------+-----------+--------+----------------+--------+----------+
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| c394fcd0-0baa-43ae-a793-201815c3e8ce | myserver1 | ACTIVE | net1=192.0.2.3 | cirros | m1.tiny |
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| 2d604e05-9a6c-4ddb-9082-8a1fbdcc797d | myserver2 | ACTIVE | net1=192.0.2.4 | ubuntu | m1.small |
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| c7c0481c-3db8-4d7a-a948-60ce8211d585 | myserver3 | ACTIVE | net1=192.0.2.5 | centos | m1.small |
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+--------------------------------------+-----------+--------+----------------+--------+----------+
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$ openstack network list
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+--------------------------------------+------+--------------------------------------+
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| ID | Name | Subnets |
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+--------------------------------------+------+--------------------------------------+
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| ad88e059-e7fa-4cf7-8857-6731a2a3a554 | net1 | 8086db87-3a7a-4cad-88c9-7bab9bc69258 |
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+--------------------------------------+------+--------------------------------------+
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Managing agents in neutron deployment
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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#. List all agents:
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.. code-block:: console
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$ openstack network agent list
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+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
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| ID | Agent Type | Host | Availability Zone | Alive | State | Binary |
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+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
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| 22467163-01ea-4231-ba45-3bd316f425e6 | Linux bridge agent | HostA | None | True | UP | neutron-linuxbridge-agent |
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| 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b | DHCP agent | HostA | None | True | UP | neutron-dhcp-agent |
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| 3066d20c-9f8f-440c-ae7c-a40ffb4256b6 | Linux bridge agent | HostB | nova | True | UP | neutron-linuxbridge-agent |
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| 55569f4e-6f31-41a6-be9d-526efce1f7fe | DHCP agent | HostB | nova | True | UP | neutron-dhcp-agent |
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+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
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Every agent that supports these extensions will register itself with the
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neutron server when it starts up.
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The output shows information for four agents. The ``alive`` field shows
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``True`` if the agent reported its state within the period defined by the
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``agent_down_time`` option in the ``neutron.conf`` file. Otherwise the
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``alive`` is ``False``.
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#. List DHCP agents that host a specified network:
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.. code-block:: console
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$ openstack network agent list --network net1
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+--------------------------------------+---------------+----------------+-------+
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| ID | Host | Admin State Up | Alive |
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+--------------------------------------+---------------+----------------+-------+
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| 22467163-01ea-4231-ba45-3bd316f425e6 | HostA | UP | True |
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+--------------------------------------+---------------+----------------+-------+
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#. List the networks hosted by a given DHCP agent:
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This command is to show which networks a given dhcp agent is managing.
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.. code-block:: console
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$ openstack network list --agent 22467163-01ea-4231-ba45-3bd316f425e6
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+--------------------------------+------------------------+---------------------------------+
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| ID | Name | Subnets |
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+--------------------------------+------------------------+---------------------------------+
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| ad88e059-e7fa- | net1 | 8086db87-3a7a-4cad- |
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| 4cf7-8857-6731a2a3a554 | | 88c9-7bab9bc69258 |
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+--------------------------------+------------------------+---------------------------------+
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#. Show agent details.
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The :command:`openstack network agent show` command shows details for a
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specified agent:
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.. code-block:: console
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$ openstack network agent show 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b
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+---------------------+--------------------------------------------------+
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| Field | Value |
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+---------------------+--------------------------------------------------+
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| admin_state_up | UP |
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| agent_type | DHCP agent |
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| alive | True |
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| availability_zone | nova |
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| binary | neutron-dhcp-agent |
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| configurations | dhcp_driver='neutron.agent.linux.dhcp.Dnsmasq', |
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| | dhcp_lease_duration='86400', |
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| | log_agent_heartbeats='False', networks='1', |
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| | notifies_port_ready='True', ports='3', |
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| | subnets='1' |
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| created_at | 2016-12-14 00:25:54 |
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| description | None |
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| last_heartbeat_at | 2016-12-14 06:53:24 |
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| host | HostA |
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| id | 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b |
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| started_at | 2016-12-14 00:25:54 |
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| topic | dhcp_agent |
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+---------------------+--------------------------------------------------+
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In this output, ``last_heartbeat_at`` is the time on the neutron
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server. You do not need to synchronize all agents to this time for this
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extension to run correctly. ``configurations`` describes the static
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configuration for the agent or run time data. This agent is a DHCP agent
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and it hosts one network, one subnet, and three ports.
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Different types of agents show different details. The following output
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shows information for a Linux bridge agent:
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.. code-block:: console
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$ openstack network agent show 22467163-01ea-4231-ba45-3bd316f425e6
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+---------------------+--------------------------------------+
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| Field | Value |
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+---------------------+--------------------------------------+
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| admin_state_up | UP |
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| agent_type | Linux bridge agent |
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| alive | True |
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| availability_zone | nova |
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| binary | neutron-linuxbridge-agent |
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| configurations | { |
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| | "physnet1": "eth0", |
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| | "devices": "4" |
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| | } |
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| created_at | 2016-12-14 00:26:54 |
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| description | None |
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| last_heartbeat_at | 2016-12-14 06:53:24 |
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| host | HostA |
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| id | 22467163-01ea-4231-ba45-3bd316f425e6 |
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| started_at | 2016-12-14T06:48:39.000000 |
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| topic | N/A |
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+---------------------+--------------------------------------+
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The output shows ``bridge-mapping`` and the number of virtual network
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devices on this L2 agent.
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Managing assignment of networks to DHCP agent
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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A single network can be assigned to more than one DHCP agents and
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one DHCP agent can host more than one network.
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You can add a network to a DHCP agent and remove one from it.
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#. Default scheduling.
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When you create a network with one port, the network will be scheduled to
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an active DHCP agent. If many active DHCP agents are running, select one
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randomly. You can design more sophisticated scheduling algorithms in the
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same way as nova-schedule later on.
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.. code-block:: console
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$ openstack network create net2
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$ openstack subnet create --network net2 --subnet-range 198.51.100.0/24 subnet2
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$ openstack port create port2 --network net2
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$ openstack network agent list --network net2
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+--------------------------------------+---------------+----------------+-------+
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| ID | Host | Admin State Up | Alive |
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+--------------------------------------+---------------+----------------+-------+
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| 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b | HostA | UP | True |
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+--------------------------------------+---------------+----------------+-------+
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It is allocated to DHCP agent on HostA. If you want to validate the
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behavior through the :command:`dnsmasq` command, you must create a subnet for
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the network because the DHCP agent starts the dnsmasq service only if
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there is a DHCP.
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#. Assign a network to a given DHCP agent.
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To add another DHCP agent to host the network, run this command:
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.. code-block:: console
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$ openstack network agent add network --dhcp \
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55569f4e-6f31-41a6-be9d-526efce1f7fe net2
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$ openstack network agent list --network net2
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+--------------------------------------+-------+----------------+--------+
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| ID | Host | Admin State Up | Alive |
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+--------------------------------------+-------+----------------+--------+
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| 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b | HostA | UP | True |
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| 55569f4e-6f31-41a6-be9d-526efce1f7fe | HostB | UP | True |
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+--------------------------------------+-------+----------------+--------+
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Both DHCP agents host the ``net2`` network.
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#. Remove a network from a specified DHCP agent.
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This command is the sibling command for the previous one. Remove
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``net2`` from the DHCP agent for HostA:
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.. code-block:: console
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$ openstack network agent remove network --dhcp \
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2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b net2
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$ openstack network agent list --network net2
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+--------------------------------------+-------+----------------+-------+
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| ID | Host | Admin State Up | Alive |
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+--------------------------------------+-------+----------------+-------+
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| 55569f4e-6f31-41a6-be9d-526efce1f7fe | HostB | UP | True |
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+--------------------------------------+-------+----------------+-------+
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You can see that only the DHCP agent for HostB is hosting the ``net2``
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network.
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HA of DHCP agents
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~~~~~~~~~~~~~~~~~
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Boot a VM on ``net2``. Let both DHCP agents host ``net2``. Fail the agents
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in turn to see if the VM can still get the desired IP.
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#. Boot a VM on ``net2``:
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.. code-block:: console
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$ openstack network list
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+--------------------------------------+------+--------------------------------------+
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| ID | Name | Subnets |
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+--------------------------------------+------+--------------------------------------+
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| ad88e059-e7fa-4cf7-8857-6731a2a3a554 | net1 | 8086db87-3a7a-4cad-88c9-7bab9bc69258 |
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| 9b96b14f-71b8-4918-90aa-c5d705606b1a | net2 | 6979b71a-0ae8-448c-aa87-65f68eedcaaa |
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+--------------------------------------+------+--------------------------------------+
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$ openstack server create --image tty --flavor 1 myserver4 \
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--nic net-id=9b96b14f-71b8-4918-90aa-c5d705606b1a
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...
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$ openstack server list
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+--------------------------------------+-----------+--------+-------------------+---------+----------+
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| ID | Name | Status | Networks | Image | Flavor |
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+--------------------------------------+-----------+--------+-------------------+---------+----------+
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| c394fcd0-0baa-43ae-a793-201815c3e8ce | myserver1 | ACTIVE | net1=192.0.2.3 | cirros | m1.tiny |
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| 2d604e05-9a6c-4ddb-9082-8a1fbdcc797d | myserver2 | ACTIVE | net1=192.0.2.4 | ubuntu | m1.small |
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| c7c0481c-3db8-4d7a-a948-60ce8211d585 | myserver3 | ACTIVE | net1=192.0.2.5 | centos | m1.small |
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| f62f4731-5591-46b1-9d74-f0c901de567f | myserver4 | ACTIVE | net2=198.51.100.2 | cirros1 | m1.tiny |
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+--------------------------------------+-----------+--------+-------------------+---------+----------+
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#. Make sure both DHCP agents hosting ``net2``:
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Use the previous commands to assign the network to agents.
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.. code-block:: console
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$ openstack network agent list --network net2
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+--------------------------------------+-------+----------------+-------+
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| ID | Host | Admin State Up | Alive |
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+--------------------------------------+-------+----------------+-------+
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| 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b | HostA | UP | True |
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| 55569f4e-6f31-41a6-be9d-526efce1f7fe | HostB | UP | True |
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+--------------------------------------+-------+----------------+-------+
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To test the HA of DHCP agent:
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#. Log in to the ``myserver4`` VM, and run ``udhcpc``, ``dhclient`` or
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other DHCP client.
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#. Stop the DHCP agent on HostA. Besides stopping the
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``neutron-dhcp-agent`` binary, you must stop the ``dnsmasq`` processes.
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#. Run a DHCP client in VM to see if it can get the wanted IP.
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#. Stop the DHCP agent on HostB too.
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#. Run ``udhcpc`` in the VM; it cannot get the wanted IP.
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#. Start DHCP agent on HostB. The VM gets the wanted IP again.
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Disabling and removing an agent
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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An administrator might want to disable an agent if a system hardware or
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software upgrade is planned. Some agents that support scheduling also
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support disabling and enabling agents, such as L3 and DHCP agents. After
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the agent is disabled, the scheduler does not schedule new resources to
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the agent.
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After the agent is disabled, you can safely remove the agent.
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Even after disabling the agent, resources on the agent are kept assigned.
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Ensure you remove the resources on the agent before you delete the agent.
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Disable the DHCP agent on HostA before you stop it:
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.. code-block:: console
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$ openstack network agent set 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b --disable
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$ openstack network agent list
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+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
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| ID | Agent Type | Host | Availability Zone | Alive | State | Binary |
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+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
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| 22467163-01ea-4231-ba45-3bd316f425e6 | Linux bridge agent | HostA | None | True | UP | neutron-linuxbridge-agent |
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|
| 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b | DHCP agent | HostA | None | True | DOWN | neutron-dhcp-agent |
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|
| 3066d20c-9f8f-440c-ae7c-a40ffb4256b6 | Linux bridge agent | HostB | nova | True | UP | neutron-linuxbridge-agent |
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|
| 55569f4e-6f31-41a6-be9d-526efce1f7fe | DHCP agent | HostB | nova | True | UP | neutron-dhcp-agent |
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|
+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
|
|
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After you stop the DHCP agent on HostA, you can delete it by the following
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command:
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|
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.. code-block:: console
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$ openstack network agent delete 2444c54d-0d28-460c-ab0f-cd1e6b5d3c7b
|
|
$ openstack network agent list
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|
+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
|
|
| ID | Agent Type | Host | Availability Zone | Alive | State | Binary |
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|
+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
|
|
| 22467163-01ea-4231-ba45-3bd316f425e6 | Linux bridge agent | HostA | None | True | UP | neutron-linuxbridge-agent |
|
|
| 3066d20c-9f8f-440c-ae7c-a40ffb4256b6 | Linux bridge agent | HostB | nova | True | UP | neutron-linuxbridge-agent |
|
|
| 55569f4e-6f31-41a6-be9d-526efce1f7fe | DHCP agent | HostB | nova | True | UP | neutron-dhcp-agent |
|
|
+--------------------------------------+--------------------+-------+-------------------+-------+-------+---------------------------+
|
|
|
|
After deletion, if you restart the DHCP agent, it appears on the agent
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|
list again.
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|
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|
.. _conf-dhcp-agents-per-network:
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|
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|
Enabling DHCP high availability by default
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|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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|
|
|
You can control the default number of DHCP agents assigned to a network
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|
by setting the following configuration option
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|
in the file ``/etc/neutron/neutron.conf``.
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|
|
|
.. code-block:: ini
|
|
|
|
dhcp_agents_per_network = 3
|