Aruba Networks PowerConnect W Clearpass 100 Software Guide de référence rapide

Amigopod

High Availability

Deployment Guide

|March 2011 Amigopod |Technical Note

Wireless Networks®, the registered Aruba the Mobile Edge Company logo, Aruba Mobility

Management System®, Mobile Edge Architecture®, People Move. Networks Must Follow®,

respective owners.

Open Source Code

Certain Aruba products include Open Source software code developed by third parties, including

software code subject to the GNU General Public License (GPL), GNU Lesser General Public License

(LGPL), or other Open Source Licenses. The Open Source code used can be found at this site:

http://www.arubanetworks.com/open_source

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The use of Aruba Networks, Inc. switching platforms and software, by all individuals or corporations,

to terminate other vendors’ VPN client devices constitutes complete acceptance of liability by that

individual or corporation for this action and indemnifies, in full, Aruba Networks, Inc. from any and all

legal actions that might be taken against it with respect to infringement of copyright on behalf of

those vendors.

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This hardware product is protected by the standard Aruba warranty of one year parts/labor. For more

information, refer to the ARUBACARE SERVICE AND SUPPORT TERMS AND CONDITIONS.

Altering this device (such as painting it) voids the warranty.

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Amigopod |Technical Note High Availability Deployment Guide |3

Table of Contents

Introduction ........................................................................................................................................ 4

Audience .......................................................................................................................................... 4

Document Overview ......................................................................................................................... 4

About High Availability....................................................................................................................... 5

Terminology & concepts................................................................................................................... 5

Network architecture........................................................................................................................ 5

Operating a High Availability cluster................................................................................................. 6

Normal cluster operation .............................................................................................................. 6

Failure detection........................................................................................................................... 7

Database replication..................................................................................................................... 7

Configuration replication .............................................................................................................. 7

Primary node failure ..................................................................................................................... 8

Secondary node failure................................................................................................................. 9

Cluster status ................................................................................................................................. 10

Technical considerations................................................................................................................ 11

Deploying an SSL certificate ...................................................................................................... 11

Configuring High Availability ........................................................................................................... 12

Check plugin versions .................................................................................................................... 12

Cluster setup.................................................................................................................................. 12

Prepare primary node................................................................................................................. 12

Prepare secondary node ............................................................................................................ 13

Cluster initialization .................................................................................................................... 14

Cluster deployment .................................................................................................................... 15

Cluster maintenance ...................................................................................................................... 15

Recovering from a failure ........................................................................................................... 15

Recovering from a temporary outage......................................................................................... 16

Recovering from a hardware failure............................................................................................ 16

Performing scheduled maintenance ........................................................................................... 17

Destroying a cluster.................................................................................................................... 18

Cluster troubleshooting .............................................................................................................. 18

4| High Availability Deployment Guide Amigopod |Technical Note

1Introduction

This technical note describes the process of setting up a high-availability cluster of

Amigopod Visitor Management Appliances.

Audience

This document is intended for network administrators and system integrators deploying an

Amigopod-based visitor management solution.

Basic familiarity with the Amigopod Visitor Management Appliance is assumed. For in-

depth information about the features and functions of the Amigopod appliance, refer to the

Amigopod Deployment Guide.

Document Overview

The first section of the document explains the architecture of an Amigopod high

availability system.

The next section contains a walkthrough and configuration guide for deploying a cluster of

Amigopod Visitor Management Appliances.

Amigopod |Technical Note High Availability Deployment Guide |5

2About High Availability

Terminology & concepts

A cluster consists of a primary node and a secondary node, configured so that a failure of

either node will not prevent the cluster as a whole from performing its normal functions.

The primary node is the active server in a cluster. The cluster’s network services are

always delivered by the primary node.

The secondary node is the backup server in a cluster. If the primary node fails, the

secondary automatically takes over and continues delivering network service.

Fault tolerance is the ability of a server cluster to continue operating if either the

primary or secondary node experiences a hardware failure.

Fail-over is the process by which the secondary node assumes control of the cluster once

the primary node has failed.

A cluster’s virtual IP address is a unique IP address that will always be assigned to the

primary node of the cluster. In order to take advantage of the cluster’s fault tolerance, all

clients that use the cluster must use the cluster’s virtual IP address, rather than each

node’s IP address.

Replication is the process of ensuring that the secondary node maintains an exact copy of

the primary node’s database contents and configuration. Replication is used to ensure that

if a fail-over is required, the secondary node can continue to deliver an uninterrupted

service to clients of the cluster.

Keep-alive is the process by which cluster failures are detected. The primary and

secondary nodes verify that each is able to communicate with the other node by sending

network requests and answering with a response.

Database replication is the process of ensuring that all changes to the database,

including new guest accounts, changes to existing guest accounts, RADIUS roles, NAS

servers, and RADIUS accounting information, are replicated from the primary node to the

secondary node. This replication process occurs continuously in a normally operating

cluster. Replication is required so that in the event of a primary node failure, the secondary

node is up to date and can continue to deliver the same network services to clients.

Configuration replication is similar to database replication, but occurs at a slower rate

due to the reduced frequency of configuration updates.

The downtime threshold is the time for which the primary node of the cluster must

remain offline before an automatic fail-over will be initiated. This is 30 seconds by default.

Network architecture

Diagram 1 shows the network architecture for a high availability cluster.

6| High Availability Deployment Guide Amigopod |Technical Note

Diagram 1: Network architecture of high availability cluster

The key points to note about this architecture are:

•The RADIUS and web server protocols (HTTP and HTTPS) are supported by the

cluster.

•The cluster has three IP addresses: each node has its own IP address, and there is a

virtual IP address for the cluster which will always be assigned to the primary node in

the cluster.

•For the cluster to provide fail-over redundancy, all network access servers and

operators must use the cluster’s IP address.

•The network administrator should use the node IP addresses to perform system

administration tasks on each node, including managing the cluster itself.

The nodes in the cluster must be connected to the same local network. Use high quality

network cables and reliable switching equipment to ensure the nodes have an

uninterrupted network connection.

NOTE There should be no routers, gateways, firewalls, or network address translation (NAT)

between the two nodes.

NOTE Having nodes in different physical locations is not recommended and is not a supported

configuration for the cluster.

Operating a High Availability cluster

Normal cluster operation

When the cluster is operating normally, the cluster status will be:

The cluster is running normally.

Amigopod |Technical Note High Availability Deployment Guide |7

In this state, the primary node is assigned the cluster IP address and is responsible for

delivering network services to clients. Each node is also continuously performing failure

detection, database replication and configuration replication, as explained below.

Failure detection

Failure detection is accomplished using a keep-alive test. The primary and secondary

nodes verify that each is able to communicate with the other node by sending network

requests and answering with a response. This takes place at the Keep Alive Rate specified

in the cluster configuration, which by default is once every 2 seconds.

If several consecutive keep-alive tests have failed, the cluster determines that a failure has

occurred. A cluster fail-over may then take place, depending on which node has failed.

Refer to section 0 for information about a primary node failure, or section 0 for

information about a secondary node failure.

To avoid any network service interruptions, it is important that the nodes maintain an

uninterrupted network connection.

Database replication

Database replication occurs continuously in a normally operating cluster. All database

modifications, including new guest accounts, changes to existing guest accounts, RADIUS

roles, NAS servers, and RADIUS accounting information, are replicated from the primary

node to the secondary node. The replication delay will depend on the volume of database

updates and system load but is generally only a few seconds.

Replicating the database contents ensures that in the event of a primary node failure, the

secondary node is up to date and can continue to deliver the same network services to

clients.

NOTE While the primary node is online, the secondary node’s database can only be updated with

replication changes from the primary node. No other database changes can take place on

the secondary node. Because of this, any form that requires a database update will be

disabled and shown as “Read Only Access” on the secondary node.

Ensure that you always access the cluster using the virtual IP address when performing

any database updates, such as creating new guest accounts or performing RADIUS

authentication. This is required so that the changes will be performed on the primary node

and then replicated to the secondary node.

Configuration replication

Configuration replication also occurs continuously within the cluster, but takes place at

a slower rate due to the reduced frequency of configuration updates. This rate is the

Config Sync rate specified in the cluster configuration, which by default is once every

minute.

8| High Availability Deployment Guide Amigopod |Technical Note

The configuration items that are replicated include:

•Configuration for installed plugins

•Fields defined in Guest Manager

•Forms and views defined in Guest Manager

•Guest self-registration pages

•Instances of reports that have previously been run

•LDAP authentication servers and translation rules

•Network login access configuration

•Operator login configuration

•Operator logins

•Operator profiles

•Print templates defined in Guest Manager

•Publicly-accessible web server items in Content Manager

•RADIUS server configuration

•Report definitions

•SMS service configuration

•SMTP server configuration

•SMTP settings for email receipts

•SNMP server settings

•The set of currently installed plugins

•Web Login pages

Certain configuration items are not replicated. These are:

•HTTP Proxy settings

•Network interface configuration

•RADIUS dictionary entries

•SSL certificate settings

•Subscription IDs in Plugin Manager

•System hostname

Primary node failure

If the cluster’s primary node fails, the cluster status will be displayed on the secondary

node as:

The secondary node is running, but the primary node is down or stopped.

Amigopod |Technical Note High Availability Deployment Guide |9

While the primary node is down, the cluster is in a failed state and cannot deliver network

services. If the primary node recovers within the downtime threshold, the cluster will

automatically return to the normal state and network service will be restored.

An automatic fail-over will be initiated after the primary node has been offline for the

downtime threshold, which is 30 seconds by default.

Once fail-over has occurred, the cluster status will be displayed on the secondary node as:

The secondary node has taken over the cluster services because the primary node is down.

In the fail-over state, the secondary node will assume control of the cluster and will take

over the cluster’s IP address. This will restore network service for clients of the cluster.

Replication will stop as there is no longer a primary node.

While the primary node is offline, the cluster will no longer be fault-tolerant. A subsequent

failure of the secondary node will leave the cluster inoperable.

Refer to section 0 for instructions on recovering a cluster in this state.

The secondary node has taken over the cluster services. The primary node is back online,

but the cluster needs to be recovered.

In this state, the primary node was offline for a period of time greater than the downtime

threshold, and then recovered. The cluster has failed over to the secondary node.

In this state, the cluster is not fault-tolerant. A subsequent failure of the secondary node

will leave the cluster inoperable.

Recovering the cluster is required for replication to resume and return the cluster to a

fault-tolerant state.

Refer to section 0 for instructions on recovering a cluster in this state.

Secondary node failure

If the cluster’s secondary node fails, the cluster status will be displayed on the primary

node as:

The primary node is running, but the secondary node is down or stopped.

The cluster will continue operating without service interruption. Network services will be

unaffected as the cluster’s virtual IP address is assigned to the primary node.

While the secondary node is offline, the cluster will no longer be fault-tolerant. A

subsequent failure of the primary node will leave the cluster inoperable.

To recover the cluster, the secondary node must be brought back online. If the node has

experienced only a temporary outage and has the same cluster configuration, the cluster

will automatically repair itself. Replication will update the secondary node with any

database or configuration changes that were made on the primary node while the

secondary node was offline.

If the secondary node was replaced due to a hardware failure then the cluster must be

destroyed and rebuilt. Refer to section 0 for instructions on recovering a cluster in this

state.

10| High Availability Deployment Guide Amigopod |Technical Note

Cluster status

The current status of the cluster is shown at the top of each page that is related to High

Availability Services.

Refer to this table for an explanation of each possible status, and the recommended action

to take, if any.

Status Description

This system is not part of a high availability cluster.

To create a new cluster and make this server the primary node, use the

Create New Cluster command.

To join a cluster and make this server the secondary node, use the Join

Cluster command.

The cluster is running normally.

Click the View details link to show more information about the cluster.

To perform a scheduled maintenance task, such as a reboot, on the

primary node in the cluster, use the Cluster Maintenance command.

Refer to section 0 for more information about normal cluster operations.

The secondary node has taken over the cluster services because the primary

node is down.

A fail-over has occurred. The cluster must be recovered to resume fault-

tolerant operation.

Ensure the primary node is back online.

The secondary node has taken over the cluster services. The primary node is

back online, but the cluster needs to be recovered.

A fail-over has occurred. The cluster must be recovered to resume fault-

tolerant operation.

Use the procedure described in section 0.

A failure has occurred.

Check the detailed status information.

If this message persists, you may need to rebuild the cluster. Refer to

section 0.

The primary node is running, but the secondary node is down or stopped.

The secondary is no longer available. Check the Remote Status on the

primary node to determine the cause of the problem.

To clear the error condition, bring the secondary node back online. The

cluster will return to fault-tolerant mode automatically.

If the secondary node needs to be replaced, the cluster must be rebuilt.

Refer to section 0.

The secondary node is running, but the primary node is down or stopped.

The primary is no longer available. Check the Remote Status on the

secondary node to determine the cause of the problem.

The cluster IP address is inaccessible and network services are

unavailable.

Automatic fail-over will take place after the downtime threshold has

been exceeded.

The cluster services are starting.

Check the detailed status information.

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