Kemp High availability User 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

1Introduction

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

2Advantages 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

3Prerequisites

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

4HA 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

5Setting 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.

High Availability (HA)

Feature Description

Figure 5-9: Confirmation message

4. Click OK on the resulting message.

Figure 5-10: Shared IP address reminder

5. Click OK on the resulting message.

Figure 5-11: Network Interface screen

6. Enter the HA Shared IP address and click the Set Shared address button.

The HA Shared IP address must be the same as the HA Shared IP

address which was set when configuring the first unit in Section 5.1.

7. Click OK on the resulting message.

8. Click OK on the message asking to reconnect to the shared IP address.

9. Enter the IP address of the first (master) unit in the HA pair in the HA Partner IP address

field and click Set Partner address.

10. Click OK on the resulting message.

11. Change any other settings as needed.

12. Click the Reboot Now button.

High Availability (HA)

Feature Description

Figure 5-12: Rebooting screen

13. Click the Continue button.

Passwords for the bal account are not synchronized across HA pairs, so

ensure to use the same password on both units. Problems may occur if

different passwords are used.

After rebooting, the HA pair will establish a TCP connection (using port 6973) between the 2

addresses. The synchronization process is started for the configuration.

The indicator squares should now show green and green. The A indicates the active unit of

the pair. If the first synchronization attempt fails (i.e. the icons are not green and green) a second

attempt might be needed.

Figure 5-13: Credentials section

On the home screen, the IP address field has changed. In addition to specifying the shared IP

address of the pair, it also specifies the active unit in the pair. The left IP address is the shared

address. The IP address in brackets is the address of the current, active unit. Next to that, the HA

version (Carp) is displayed.

High Availability (HA)

Feature Description

5.3 Enable the “Use for HA Checks” Option

Some guidelines relating to the Use for HA checks option are below:

If you have a physical LoadMaster, you can connect a direct cable on eth1 between both

boxes. Leave the IP configuration blank. Select the Use for HA checks check box.

In a hardware configuration, if a direct cable has been deployed between both units over

eth1 and there are IP addresses set in the interface management screen (and Use for HA

checks is enabled on that interface) this causes problems because the LoadMaster will

think it is a production link and if one of the LoadMasters reboot the other will fail too.

If the Use for HA checks check box is greyed out it means that this is the only interface

configured to be used for HA checks and cannot be deselected.

To enable the Use for HA checks option, follow the steps below:

1. Go to the WUI of the shared IP address.

2. In the main menu, select System Configuration.

3. Select the relevant interface.

4. Select the Use for HA checks check box.

These steps can be repeated if the Use for HA checks option needs to be enabled on more than

one interface.

5.4 Test Failover

Now that the HA units have been set up, failover can be tested if needed. The easiest way to do

this is to reboot the active unit. To reboot the unit, follow the steps below:

1. Log in to the IP address of the active unit.

2. In the main menu, click Local Administration.

3. Select System Reboot.

Figure 5-14: System Reboot screen

4. Click the Reboot button.

High Availability (HA)

Feature Description

Figure 5-15: Confirmation message

5. A confirmation message may appear. Click OK.

Figure 5-16: Rebooting screen

6. Click Continue.

When HA1 is back online, both HA status icons should be green. The A should have moved into

the right green square. This means that the secondary unit is now the active unit.

High Availability (HA)

Feature Description

6How to Perform a Firmware Update on HA Pairs

KEMP recommends that firmware updates are performed outside of working hours. This is to

ensure there is no interruption to client connectivity. If it has to be done during working hours

we suggest that a window of maintenance is put in place.

Before updating the firmware, ensure that the Switch to Preferred Server

drop-down list is set to No Preferred Host in System Configuration >

Miscellaneous Options > HA Parameters.

To update the firmware on a HA pair; perform the following steps via the shared IP address:

1. Update the currently active LoadMaster (“A”).

2. When the update is complete, reboot A so that the passive unit becomes active.

3. When the first unit is back up, update the other unit.

4. When the update is complete, reboot other unit.

Now A should be active as it originally was.

High Availability (HA)

Feature Description

7HA Disaster Recovery Process (Replacing a Defective

Unit)

In a disaster recovery scenario you may need to replace one of the HA units. Prerequisites and

installation steps for this scenario are provided in the sections below.

7.1 Prerequisites

There are some prerequisites that are needed before replacing a HA unit in a disaster recovery

situation. These are listed below:

The new LoadMaster should be licensed:

Verify that the license is valid for the relevant features

Gather the following data:

IP address of the LoadMaster

IP address of the partner

Shared IP address

7.2 Installation

Installation of a new HA unit should be performed during a maintenance window. Allow

approximately 20 minutes for the installation.

Follow the steps below:

1. Ensure that the HA ports are connected and both machines can reach each other by

using the Ping option in System Configuration > Logging Options > System Log Files >

Debug Options.

2. Connect to the WUI on the local (machine) IP address of the new LoadMaster.

3. In the main menu of the WUI, select System Configuration > Miscellaneous Options >

HA Parameters.

Figure 7-1: HA Mode

4. Select the relevant HA Mode (first or second).

5. Click OK.

6. Click OK again.

Figure 7-2: Network Interface

High Availability (HA)

Feature Description

7. Enter the HA Shared address. Click Set Shared address.

8. Enter the HA Partner IP address. Click Set Partner address.

9. Click Reboot Now.

10. Wait 45 to 60 seconds, then click Continue.

11. Wait until the HA icons at the top of the screen are green.

12. If not yet done, connect the LoadMaster to the Real Server network and the open

network side.

13. In the main menu, select Local Administration > System Reboot.

Figure 7-3: Reboot

14. Click Reboot.

15. Click OK.

16. Click Continue.

It is optional, but KEMP recommends simulating a failover to the newly restored partner to

check that everything is working OK. There are two ways to do this, both are detailed in the

sections below.

7.2.1 Reboot the Active Unit

Rebooting the active unit should cause the new unit to take over. To do this, follow the steps

below in the WUI of the active unit:

1. In the main menu of the WUI, select Local Administration > System Reboot.

Figure 7-4: Reboot

2. Click Reboot.

3. Wait 45 to 60 seconds, then click Continue.

High Availability (HA)

Feature Description

7.2.2 Change the Switch to Preferred Server Option

To change the Switch to Preferred Server option, follow the steps below in the WUI of the

shared IP address:

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

Parameters.

Figure 7-5: HA Parameters

2. In the Switch to Preferred Server drop-down list, select the relevant option in order to set

the new LoadMaster as the preferred master.

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