6fed35279e
Reduced repetition of the term Networking, and adjusted sentence structure to improve clarity - edits centred on sentences about the external network in particular. Change-Id: Id6e03196c4d5f00dd8023b0f8d6ac3219176ca96 backport: none Closes-Bug: #1325798
64 lines
3.7 KiB
XML
64 lines
3.7 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<section 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="neutron-concepts">
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<title>Networking concepts</title>
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<para>OpenStack Networking (neutron) manages all networking facets
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for the Virtual Networking Infrastructure (VNI) and the access
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layer aspects of the Physical Networking Infrastructure (PNI) in
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your OpenStack environment. OpenStack Networking enables tenants
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to create advanced virtual network topologies including services
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such as <glossterm baseform="firewall">firewalls</glossterm>,
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<glossterm baseform="load balancer">load balancers</glossterm>,
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and <glossterm baseform="virtual private network (VPN)">virtual
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private networks (VPNs)</glossterm>.</para>
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<para>Networking provides the networks, subnets, and routers object
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abstractions. Each abstraction has functionality that mimics its
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physical counterpart: networks contain subnets, and routers route
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traffic between different subnet and networks.</para>
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<para>Each router has one gateway that connects to a network, and
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many interfaces connected to subnets. Subnets can access machines
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on other subnets connected to the same router.</para>
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<para>Any given Networking set up has at least one external network.
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Unlike the other networks, the external network is not merely a
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virtually defined network. Instead, it represents a view into a
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slice of the physical, external network accessible outside the
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OpenStack installation. IP addresses on the external network are
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accessible by anybody physically on the outside network. Because
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the external network merely represents a view into the outside
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network, DHCP is disabled on this network.</para>
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<para>In addition to external networks, any Networking set up has
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one or more internal networks. These software-defined networks
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connect directly to the VMs. Only the VMs on any given internal
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network, or those on subnets connected through interfaces to a
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similar router, can access VMs connected to that network
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directly.</para>
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<para>For the outside network to access VMs, and vice versa, routers
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between the networks are needed. Each router has one gateway that
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is connected to a network and many interfaces that are connected
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to subnets. Like a physical router, subnets can access machines on
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other subnets that are connected to the same router, and machines
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can access the outside network through the gateway for the
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router.</para>
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<para>Additionally, you can allocate IP addresses on external
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networks to ports on the internal network. Whenever something is
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connected to a subnet, that connection is called a port.You can
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associate external network IP addresses with ports to VMs. This
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way, entities on the outside network can access VMs.</para>
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<para>Networking also supports <emphasis role="italic">security
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groups</emphasis>. Security groups enable administrators to
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define firewall rules in groups. A VM can belong to one or more
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security groups, and Networking applies the rules in those
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security groups to block or unblock ports, port ranges, or traffic
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types for that VM.</para>
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<para>Each plug-in that Networking uses has its own concepts. While
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not vital to operating the VNI and OpenStack environment,
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understanding these concepts can help you set up Networking.
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All Networking installations use a core plug-in and a security group
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plug-in (or just the No-Op security group plug-in). Additionally,
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Firewall-as-a-Service (FWaaS) and Load-Balancer-as-a-Service (LBaaS)
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plug-ins are available.</para>
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</section>
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