64 lines
3.7 KiB
XML
64 lines
3.7 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0"
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xml:id="module002-ch002-openstack-networking-concepts">
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<title>OpenStack Networking Concepts</title>
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<para><emphasis role="bold">Network Types</emphasis></para>
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<para>The OpenStack Networking configuration provided by the
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Rackspace Private Cloud cookbooks allows you to choose between
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VLAN or GRE isolated networks, both provider- and
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tenant-specific. From the provider side, an administrator can
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also create a flat network.</para>
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<para>The type of network that is used for private tenant networks
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is determined by the network_type attribute, which can be
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edited in the Chef override_attributes. This attribute sets
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both the default provider network type and the only type of
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network that tenants are able to create. Administrators can
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always create flat and VLAN networks. GRE networks of any type
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require the network_type to be set to gre.</para>
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<para><emphasis role="bold">Namespaces</emphasis></para>
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<para>For each network you create, the Network node (or Controller
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node, if combined) will have a unique network namespace
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(netns) created by the DHCP and Metadata agents. The netns
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hosts an interface and IP addresses for dnsmasq and the
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quantum-ns-metadata-proxy. You can view the namespaces with
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the ip netns [list], and can interact with the namespaces with
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the ip netns exec <namespace> <command>
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command.</para>
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<para><emphasis role="bold">Metadata</emphasis></para>
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<para>Not all networks or VMs need metadata access. Rackspace
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recommends that you use metadata if you are using a single
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network. If you need metadata, you may also need a default
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route. (If you don't need a default route, no-gateway will
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do.)</para>
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<para>To communicate with the metadata IP address inside the
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namespace, instances need a route for the metadata network
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that points to the dnsmasq IP address on the same namespaced
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interface. OpenStack Networking only injects a route when you
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do not specify a gateway-ip in the subnet.</para>
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<para>If you need to use a default route and provide instances
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with access to the metadata route, create the subnet without
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specifying a gateway IP and with a static route from 0.0.0.0/0
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to your gateway IP address. Adjust the DHCP allocation pool so
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that it will not assign the gateway IP. With this
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configuration, dnsmasq will pass both routes to instances.
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This way, metadata will be routed correctly without any
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changes on the external gateway.</para>
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<para><emphasis role="bold">OVS Bridges</emphasis></para>
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<para>An OVS bridge for provider traffic is created and configured
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on the nodes where single-network-node and single-compute are
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applied. Bridges are created, but physical interfaces are not
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added. An OVS bridge is not created on a Controller-only
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node.</para>
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<para>When creating networks, you can specify the type and
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properties, such as Flat vs. VLAN, Shared vs. Tenant, or
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Provider vs. Overlay. These properties identify and determine
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the behavior and resources of instances attached to the
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network. The cookbooks will create bridges for the
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configuration that you specify, although they do not add
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physical interfaces to provider bridges. For example, if you
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specify a network type of GRE, a br-tun tunnel bridge will be
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created to handle overlay traffic.</para>
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</chapter> |