VI. Feature Setup

High Availability - Frequently Asked Questions

Products:
Vigor 2860
Vigor 2862
Vigor 2865
Vigor 2925
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Keywords:
Configuration Sync
High Availability
Hot Standby
backup
Show all


DrayTek's High Availability facility allows two or more DrayTek routers to be setup in a master / slave configuration; if the active router were to stop responding, a backup router can resume connectivity without requiring human intervention. The primary (master) unit normally provides the Internet connectivity but, in the case of hardware or WAN connectivity failure, the secondary (backup) router automatically kicks-in and takes over Internet connectivity. Depending on the configuration, the master/slave routers could access the same Internet connections, or each have their own independent connection (see active vs. hot question later).

This guide is intended to cover commonly asked questions regarding requirements and miscellaneous setup of High Availability, with the following sections:

General Questions

1. Which routers support High Availability?

  • Vigor 2860 Router - Requires 3.8.4 or later firmware
  • Vigor 2862 Router
  • Vigor 2865 Router
  • Vigor 2925 Router - Requires 3.8.2 or later firmware
  • Vigor 2926 Router
  • Vigor 2927 Router
  • Vigor 2952 Router
  • Vigor 2960 Router
  • Vigor 2962 Router
  • Vigor 3220 Router
  • Vigor 3900 Router
  • Vigor 3910 Router

2. What is the difference between Active Standby and Hot Standby?

Both modes use a Virtual IP on the LAN for clients to use as a gateway.

Hot Standby mode is designed for two or more routers, with the backup router(s) remaining in standby unless the primary router fails. The backup routers can still be managed on the network but they will not provide network or VPN connectivity. Only the active router will be operating as the network gateway. The routers in the High Availability group must have the same WAN interfaces. This mode has the option of using the Configuration Sync feature to keep the backup router configurations in sync with the active router. This method also allows sharing a Web Content Filtering license between the group.

Active Standby mode is designed for router configurations that have different internet connections. The backup router(s) will still be connected to their respective internet connections and can provide Internet Access or VPN connectivity where required. The Primary / Active router will take ownership of the Virtual IP on the LAN for clients to use as a gateway.

3. Is any additional licensing required to use High Availability

No, if the router supports the feature, it can be used with no additional cost or license required.

4. How do two routers share a single internet connection?

Both routers must be physically connected to the shared internet connection. With Ethernet WAN interfaces, this may require the use of a switch for the routers to share the same Ethernet WAN interface or modem (such as the Vigor 130 modem).
Only the Primary / Active router will dial the PPPoE connection or use the WAN IP (Static / Dynamic IP).
The backup router(s) will retain a physical connection but will not dial a PPPoE connection or use the WAN interface until it has taken ownership of the Virtual IP.

5. Can two routers share a VDSL2 or ADSL2+ line?

Only if they're both connected to a separate VDSL modem such as the Vigor 130.
A Vigor 130 modem (or other xDSL modem) providing the xDSL connection to a pair of Vigor 2860 routers each using their Ethernet WAN2 port would allow sharing of a single xDSL connection.

Only the Vigor 2860 will support High Availability while directly connected to a VDSL2 / ADSL2+ line. It is not currently possible for two Vigor 2860 routers using their WAN1 DSL port to share a VDSL / ADSL line because each router needs to be able to sync with the DSL line to determine whether it is operational and with DSL, only one device can be physically connected to the line at any one time.

One solution for this would be to use Active Standby mode, which can use two xDSL lines for the router pair allowing each router to use their respective xDSL Internet connection.

Using High Availability in Hot Standby mode using the Vigor 2860's WAN1 interface would require two xDSL lines that have the same credentials. The WAN connection on the 2nd xDSL line would be unused until a failover occurs.

6. Can two different model routers, such as a Vigor 2925 and a Vigor 2960 be used in a High Availability Group?

It is not currently possible to use different model routers in a High Availability group.

At this time, it is not possible to use routers of the same series but with different features i.e. a Vigor 2860 and a Vigor 2860n with High Availability. Both routers must have the same suffix.

7. Can routers in a High Availability group use the same Web Content Filtering license?

This is possible when using High Availability in Hot Standby mode, because only one router would be providing internet access and content filtering at a time. This requires configuration on the MyVigor site and all routers in the HA group must be on the same MyVigor account. The setup of this facility is explained in-depth in the Hot Standby setup guide.

8. How many nodes / licenses are required in Vigor ACS-SI for a High Availability group?

If using Hot Standby mode, there will be a single active router at any one time and ACS will consider the active device to be a single node and the standby routers will not count as active Vigor ACS-SI nodes.

If using Active Standby mode, each router will be active and will count as an active Vigor ACS-SI node.

Setup

1. How does the Priority ID setting work for deciding which router is the Primary?

The router with the highest number Priority ID value has the highest priority and will be the Primary router. If two routers have the same Priority ID value, the priority is then decided by the LAN 1 IP address - the router with the lower number IP address will have higher priority. 

For Example:
Router 1 has an IP of 192.168.1.2
Router 2 has an IP of 192.168.1.3

If they both have the same Priority ID value, Router 1 has the lower number IP address and becomes the Primary router.

2. What is the Group ID number used for?

A single network can have multiple High Availability groups, this is used to allow multiple groups to co-exist on the same network.

3. What would the Update DDNS option be used for?

If the internet connections used by the High Availability group have dynamic IP addresses, this option can be enabled so that the secondary router will update the IP address with a Dynamic DNS provider configured under [Applications] > [Dynamic DNS].

4. Is there a recommended way to connect routers in a High Availability group?

Connectivity between the HA router group is essential, if this is interrupted, for example the switch connecting the routers loses power or restarts, it may cause a failover to occur while the primary router is still operational.

One suggestion is to configure one of the LAN ports on each router to operate on a separate VLAN and connect a network cable between that dedicated VLAN. This VLAN would then be select as the Management Interface of the High Availability group. This interface must be separate from the main network (using a direct cable connection or a dedicated switch) to avoid a network loop. The other LAN ports on the router can be connected to the main network.

Another possible configuration is to set up a separate switch for High Availability usage only. This would be connected between the routers on a dedicated VLAN as with the previous suggestion.

Usage

1. What conditions will cause High Availability to fail over to a Secondary router?

Any of the following:

  • If all WAN interfaces on the Active router are disconnected
  • If the Secondary router(s) do not receive DARP (DrayTek Address Redundancy Protocol) updates from the Active router (i.e. Primary router has lost power)
  • If connectivity is lost on the High Availability Management interface between the Active and Secondary routers

When the Primary / Highest priority router resumes service on the network, the Secondary router will go back into a standby state so that the Primary router can resume service.

2. What does the Stable state indicate?

This shows the state of the High Availability negotiation; if the HA settings have changed or a router is restarted, it will initially display "No" for the Stable state. Once the Primary / Highest priority router has been determined for the High Availability group, this will display "Yes" for the Stable state.

3. Do the routers share state information, such as NAT table, DHCP table?

The routers share WAN and LAN status information to determine whether the routers have LAN and internet connectivity using DARP (DrayTek Address Redundancy Protocol). This does not currently include NAT session information or DHCP leases.

If a failover occurs, clients would be able to make new sessions and resume connectivity. DHCP leases provided by the Backup router will not conflict with leases provided by the Primary router.

4. Can the wireless interface of the Secondary router(s) be used?

When the routers are in a Hot Standby High Availability group, the wireless interface on the secondary router(s) will be disabled, unless a failover occurs, in which case, the wireless interface is activated on the router that becomes active.

Routers in an Active Standby group can still make use of the wireless interface of the secondary router(s) while they are operating as backup routers.

Config Sync

1. What is Config Sync?

It is a method to synchronise the full configuration of the Primary / active router to all secondary / backup routers, so that if a failover occurs, the functionality of the backup routers will be the same as the primary routers. This includes settings such as NAT Port Forwards, Firewall settings, Wireless network settings and VPN profiles.

2. Can Configuration Sync be used with two different models of router?
i.e. A Vigor 2925n-Plus and a Vigor 2925

This is not supported at this time, both routers must be the same Model name and they must have the same suffix.

3. Which settings remain unique to each router when using Config Sync

The following settings are not changed on the secondary / backup routers when a Config Sync is performed, these settings remain specific to each router:

DrayOS Routers i.e. Vigor 3910 & Vigor 2862

    • [LAN] > [General Setup] > [LAN/DMZ Details Page]
        Network Configuration for NAT Usage
        - IP Address
        - Subnet Mask
        DHCP Server Configuration
        - Gateway IP Address - This will automatically set to the Virtual IP for the LAN (if enabled on that LAN interface)
        IPv6 Setup
        - Static IPv6 Address
    • [Applications] > [High Availability]
    • [System Maintenance] > [Management]
      - Router Name
    • [System Maintenance] > [Administrator Password]
    • [System Maintenance] > [User Password]
    • [Objects Setting] > [SMS / Mail Service Object] > [SMS Provider] > [Quota]

Vigor 3900 & 2960

    • Applications] > [High Availability]
    • [LAN] > [General Setup]
              - Network Configuration Usage For NAT Usage
                  - IP Address
              - DHCP Server Configuration
                  - Gateway IP Address
    • [System Maintenance] > [Management] > [Router Name]

4. If changes are made to a Secondary router, are they propagated to the Primary router?

No, when the Config Sync interval occurs, the changes will be over-written with the configuration from the Primary router.


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