mirror of https://github.com/apache/cloudstack.git
74 lines
4.3 KiB
XML
74 lines
4.3 KiB
XML
<?xml version='1.0' encoding='utf-8' ?>
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<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % BOOK_ENTITIES SYSTEM "cloudstack.ent">
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%BOOK_ENTITIES;
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]>
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<!-- Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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<section id="elastic-ip">
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<title>About Elastic IP</title>
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<para>Elastic IP (EIP) addresses are the IP addresses that are associated with an account, and act
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as static IP addresses. The account owner has the complete control over the Elastic IP addresses
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that belong to the account. You can allocate an Elastic IP to a VM of your choice from the EIP
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pool of your account. Later if required you can reassign the IP address to a different VM. This
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feature is extremely helpful during VM failure. Instead of replacing the VM which is down, the
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IP address can be reassigned to a new VM in your account. Similar to the public IP address, EIPs
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are mapped to their associated private IP addresses by using StacticNAT.</para>
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<para>The EIP work flow is as follows:</para>
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<itemizedlist>
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<listitem>
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<para>When a user VM is deployed, a public IP is automatically acquired from the pool of
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public IPs configured in the zone. This IP is owned by the VM's account.</para>
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</listitem>
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<listitem>
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<para>Each VM will have its own private IP. When the user VM starts, the public IP is mapped
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to the private IP of the VM by using StaticNAT.</para>
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</listitem>
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<listitem>
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<para>This default public IP will be released in two cases:</para>
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<itemizedlist>
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<listitem>
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<para>When the VM is stopped. When the VM starts, it again receives a new public IP, not
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necessarily be the one allocated initially, from the pool of Public IPs.</para>
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</listitem>
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<listitem>
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<para>The user acquires a public IP. This public IP associated with the account will not
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be mapped to any private IP. However, the user can enable StaticNAT to associate this IP
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to the private IP of a VM in the account. The StaticNAT rule for the public IP can be
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disabled at any time. When StaticNAT is disabled, a new public IP is allocated from the
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pool, which is not necessarily be the one allocated initially.</para>
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</listitem>
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</itemizedlist>
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</listitem>
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</itemizedlist>
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<para>However, for the deployments where public IPs are limited resources, you have the
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flexibility to choose not to allocate a public IP by default. From &PRODUCT; 3.0.6 onwards, you
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can use the Associate public IP option to turn on or off the automatic public IP assignment in
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the EIP-enabled Basic zones. If you turn off the automatic public IP assignment while creating a
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network offering, only a private IP is assigned to a VM when it's deployed with the same network
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offering. Later, the user can acquire an IP for the VM and enable staticNAT. The <xref
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linkend="creating-network-offerings"/> section gives you more information on the Associate
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public IP option.</para>
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<note>
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<para>The Associate public IP feature is designed only for the user VMs. The System VMs continue
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to get both public IP and private by default irrespective of the network offering
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configuration. </para>
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</note>
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<para>In the case of new deployments, which uses the default shared network offering with EIP
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and ELB services to create shared network in the Basic zone, will continue allocating public IPs
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to each user VMs.</para>
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</section>
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