Kemp High Availability, LoadMaster High Availability Feature Description And Operation Manual

High Availability (HA)

Feature Description

High Availability

(HA)

Feature Description

VERSION: 1.7

UPDATED: JUNE 2014

High Availability (HA)

Feature Description

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High Availability (HA)

Feature Description

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Used, under license, U.S. Patent Nos. 6,473,802, 6,374,300, 8,392,563, 8,103,770, 7,831,712, 7,606,912, 7,346,695, 7,287,084 and 6,970,933

High Availability (HA)

Feature Description

Table of Contents

1 Introduction .................................................................................................................................... 6

1.1 Intended Audience .................................................................................................................. 6

2 Advantages of High Availability (HA) .............................................................................................. 7

3 Prerequisites ................................................................................................................................... 8

4 HA Components .............................................................................................................................. 9

5 Setting Up HA ................................................................................................................................ 10

5.1 Set up the First Unit .............................................................................................................. 10

5.2 Set Up the Second Unit ......................................................................................................... 12

5.3 Enable the “Use for HA Checks” Option ............................................................................... 15

5.4 Test Failover .......................................................................................................................... 15

6 How to Perform a Firmware Update on HA Pairs ......................................................................... 17

7 HA Disaster Recovery Process (Replacing a Defective Unit) ......................................................... 18

7.1 Prerequisites ......................................................................................................................... 18

7.2 Installation ............................................................................................................................ 18

7.2.1 Reboot the Active Unit .................................................................................................. 19

7.2.2 Change the Switch to Preferred Server Option ............................................................ 20

8 HA WUI Options ............................................................................................................................ 21

8.1.1 Interfaces ...................................................................................................................... 21

8.1.2 HA Parameters .............................................................................................................. 22

9 Troubleshooting ............................................................................................................................ 26

9.1 General Troubleshooting Tips ............................................................................................... 26

9.2 No HA Status Squares are Visible in the WUI ....................................................................... 26

9.3 Green/Red HA Status Squares .............................................................................................. 26

9.4 Blue HA Status Square .......................................................................................................... 27

9.5 Both Units are Active and the WUI is Unresponsive – Blue or Red Status Square ............... 27

9.6 Grey HA Status Square .......................................................................................................... 27

9.7 Virtual Services Temporarily Unavailable After Failover ...................................................... 27

9.8 No Access to WUI on HA1/2 or Shared ................................................................................. 28

9.9 Nothing Works ...................................................................................................................... 28

9.10 Issue with Hyper-V and HA on a Pair of VLMs ...................................................................... 28

High Availability (HA)

Feature Description

9.11 HA Issue on VMware ............................................................................................................. 28

9.11.1 Both Units Think That They Are the Master Unit .......................................................... 28

9.11.2 Two Virtual LoadMasters on Different Hosts ................................................................ 30

10 Replacing HA Units .................................................................................................................... 31

References ............................................................................................................................................ 36

Document History ................................................................................................................................. 37

High Availability (HA)

Feature Description

1 Introduction

The LoadMaster system can be deployed as a single unit or in an active/standby dual-unit configuration (HA). HA allows two physical or virtual machines to become one logical device. Only one of these units is active and handling traffic at any one time. One unit is active and the other is a hot standby (passive). This provides redundancy and resiliency, meaning if one LoadMaster goes down for any reason, the hot standby can become active, therefore avoiding any downtime.

HA in the LoadMaster for Azure product works a different way to that of a

regular LoadMaster. For more information and instructions on how to

configure HA on the LoadMaster for Azure, refer to the HA for Azure,

Feature Description document.

Three IP addresses are needed per active interface; one for the active unit, one for the passive unit and one IP address for the shared interface.

1.1 Intended Audience

This document is intended to be read by anyone who is interested in learning about the HA feature in the KEMP LoadMaster.

High Availability (HA)

Feature Description

2 Advantages of High Availability (HA)

Figure 2-1: Typical 1-armed HA-setup

The ultimate goal of redundant LoadMasters is to provide reliable traffic management, even if one LoadMaster becomes unavailable. The advantages of HA are as follows:

 Eliminates a single point of failure  The second (passive) unit monitors the active unit to detect if a failure has occurred  Active connections and sessions are not lost when a fail-over occurs

High Availability (HA)

Feature Description

3 Prerequisites

There are some prerequisites to be aware of before setting up HA:

 Two LoadMasters must be set up and licensed  LoadMasters must be located on the same subnet in order to be in a HA pair  LoadMasters must be in the same physical location  A layer 2 connection (Ethernet/VLAN) is required  The LoadMasters must not be located further than 100 meters from each other  Ensure that you have more than one interconnection between the two LoadMasters to

avoid data or lack of availability

 The two LoadMasters need the same default gateway  Use Network Time Protocol (NTP) to keep times on LoadMasters up-to-date. This

ensures that the times will be correct on any logs and that Common Address Redundancy Protocol (CARP) message timestamps are in sync.

 Ensure that any switches do not prevent MAC spoofing  Latency on the link between the two LoadMasters must be below 100 milliseconds  Multicast traffic flow is required in both directions between the devices  The appropriate LoadMaster license should be in place  Three IP addresses are required for each subnet in which the LoadMaster is configured

High Availability (HA)

Feature Description

4 HA Components

The HA components are listed and described below.

CARP:

 Keeps updated on the health of the partner  Governs whether the LoadMaster will take the active role  The Use for HA Checks option enables CARP requests to be sent over enabled interfaces.

This can be set for multiple interfaces.

When CARP is being used, packet analysis tools such as Wireshark, incorrectly displays the protocol used as Virtual Router Redundancy

Protocol (VRRP). Any IP addresses displayed by the packet analysis tools

are fictitious and are not part of the CARP protocol.

Sync:

 Sync maintains a “single image view” of the LoadMaster settings. It keeps the

LoadMaster up-to-date with changes made to Virtual Services and all other configurations.

 Notable exceptions that are not synchronized are; time and passwords  Keeps the standby LoadMaster updated on persistence updates

High Availability (HA)

Feature Description

5 Setting Up HA

5.1 Set up the First Unit

To build a HA LoadMaster environment there are a number of settings that must be carefully specified. Follow the steps below to set up HA:

1. Log in to the LoadMaster that is desired to be the active (master) unit.

2. In the main menu, select the System Configuration > Miscellaneous Options > HA

Parameters option.

Figure 5-1: HA Mode option

3. Select HA (First) Mode in the HA Mode drop-down.

Figure 5-2: HA question

4. Click OK on the resulting message.

Do not reboot at this time.

Figure 5-3: Shared IP address reminder

5. Click OK on the resulting message reminding not to forget to set the Shared IP address.

Figure 5-4: HA settings

High Availability (HA)

Feature Description

6. Specify the desired shared IP address in the HA Shared IP address field and click Set

Shared Address.

7. A confirmation message may appear. Click OK.

8. A message may appear asking to reconnect to the shared IP address. Click OK.

Do not reboot or reconnect at this time.

9. Enter the IP address of the passive (slave) unit in the HA Partner IP address and click the

Set Partner address button.

10. A confirmation message will appear. Click OK.

11. Configure any other settings as needed.

12. Click Reboot Now.

Figure 5-5: Rebooting message

13. Click Continue.

14. Refresh the page after the LoadMaster has rebooted (this may take a few minutes).

Figure 5-6: Log in screen

A log in screen appears. After logging in, a different menu will appear than

before. This is the Local Administration menu displayed for HA units.

This menu has far fewer options. Only configuration settings pertaining to

that specific unit are accessible via the Local Administration option. All

management of the HA units should be done via the shared IP address. To see the full menu and configure the units, access the WUI of the shared IP

address, which was specified above.

15. Log in to the shared IP WUI by entering the shared IP address in the address bar of the

browser and pressing Enter.

In the top-left of the screen there will be 2 indicator squares. These squares indicate the status of the HA pair. The left square always represents HA1 and the right represents HA2. The A represents which unit is active. The first or second HA unit can be opened by clicking the relevant status icon. Green and green status colors indicate a properly paired configuration.

High Availability (HA)

Feature Description

Currently, they will probably be green and red since the HA2 unit has not yet joined the pair. For an explanation of all icon colors and statuses, refer to Section 8.1.2.

16. Go to HA Parameters in the main menu.

Figure 5-7: HA Parameters

17. Enter a different number (different from the IDs of other HA devices) in the HA Virtual

ID text box and click Set Virtual ID. Using the same ID as other HA devices may cause

problems.

KEMP highly recommends using a higher value than 10, as any other HA

device using the same ID could interfere with HA operations.

5.2 Set Up the Second Unit

Now that HA has been configured on the first unit, the second unit needs to be setup. Follow the steps below to do this.

1. Enter the IP address of the second unit in the address bar of the browser and press

Enter.

Ensure to enter https:// before the IP address.

2. In the main menu, select the System Configuration > Miscellaneous Options > HA

Parameters option

Figure 5-8: HA Parameters screen

3. Select HA (Second) Mode as the HA Mode.

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