ALIF: Network Redundancy Example


Configuring Infinity in multi-subnet mode requires in-depth networking knowledge of VLAN and multicast routing. Whilst we can offer guidance, it is the responsibility of the installer to ensure that the network switches are provisioned and configured correctly. Please read the Successful Implementation guide that explains the switch requirements and general configuration. AIM Version 4.5 (or above) will be required for full redundancy.

The following information is a basic outline for setting up network redundancy on Infinity, that allows a network switch or AIM to fail and Infinity to continue to work. This is a guide and does not include is the actual switch configuration since there are different makes and models. The switch configuration is the responsibility of the installer.

Basic Setup

Infinity NetworkRedundancy1

  • Minimum 2x Network Switches. The switches must support IP/VLAN routing.
  • The copper and SFP ports on each end point (TX & RX) are split between the two pairs of network switches.
  • The Primary and Secondary AIM’s are connected to different network switch pairs.
  • A single fibre or copper link connection between the two switches to only carry communication between the two AIM Servers and AIM communication on the Endpoints (not multicast traffic)
  • A DHCP Server is required for each VLAN.

VLAN Setup

Three VLAN’s are required to separate the network, each with its own network range.

For example: -

VLAN Network Range Devices
1 10.0.10.x Primary and Backup AIM Servers. There is a link between the two pairs of stacked network switches that carries the communication between the AIM Servers.
2 10.0.20.x The Copper network connections from the Endpoints (TX & RX). Requires multicast (IGMP) setup.
3 10.0.30.x The SPF (converted to Copper) network connections from the Endpoints. Requires multicast (IGMP) setup.

VLAN Routing

An IP address must be setup on each VLAN, this is used as a gateway between the VLAN’s. VLAN 1 will have two IP Addresses, one for each switch/stack.

A static route must be configured on each switch to ensure that traffic is directed appropriately for VLAN 1 to VLAN’s 2 and 3. For example, on switch 1 that contains VLAN 1 and VLAN 2, a static route must be able to forward traffic to VLAN 3 on switch 2. The same will go for the switch 2 that contains VLAN 1 and VLAN 3, this should have a static route for VLAN 2 on switch 1.

For example: -

Switch VLAN IP
Switch 1: VLAN 1 IP
Static Route IP to
Switch 2: VLAN 1 IP
Static Route IP to

Network Traffic Rules

The following IP traffic rules must be configured to avoid non-AIM traffic (multicast) to pass across the single network link between the network switch pairs.

  • VLAN’s 2 and 3 must not see each other.
  • VLAN 1 is accessible on both VLAN 2 and VLAN3.
  • Allow DHCP Traffic on each VLAN

Setting up the AIM

The AIM can either act as a DHCP Server or rely on an external DHCP Server. For this configuration topology, AIM requires the use of an external DHCP server which we call Subnet Operation. The Subnet operation option can only be chosen when initially configuring the network setting on the AIM which is located under Dashboard -> Settings > Network. If you do not set this feature at the outset, you will need to factory reset the AIM including Resetting the Servers IP address and Deleting the security certificate and keys which you will find under Dashboard -> Settings -> Reset AIM Configuration.

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In addition to enabling the Subnet Operation feature, under Dashboard -> Settings -> Network you need to enable Separate Device Networks. This is to allow the two network ports to operate on different subnets.

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DHCP Setup

Now that the AIM manager is in multi-subnet mode, it is not providing the end points with a network configuration, therefore an external DHCP server is required for each VLAN.

DHCP for VLAN’s 2 and 3

The DHCP Server must support option 125 which is a vendor specific feature, that allows us to provide additional configuration information the endpoints when requesting an IP address.

The specially formatted option is used to tell an end point the IP address of the Primary and any other Backup or Satellite AIM managers that reside on the network. Further information and instructions on setting up option 125 can be found in the AIM manager manual, see the “Using DHCP Option 125” section.


Although the AIM managers main Ethernet 1 port is configured with static IP addresses, a DHCP Server is required to add classless static routes to the AIM to access the VLAN’s. When the AIM boots, it will do an ‘inform’ request to a DHCP Server on the network to gather any options that may have been set.

NOTE: An inform request simply asks for the DHCP settings but does not actually take an IP address. Not all DHCP Servers support ‘inform’ requests.

Classless static routes are defined using DHCP Option 121, and its configuration is dependent on the DHCP Server used.

Below is an example Microsoft DHCP Server configuration: -

Infinity NetworkRedundancy4

In this example, we define that all connections to VLAN2 on the 10.0.20.x network are routed to and those to VLAN3 on the 10.0.30.x network are routed to for on the second network switch.

Example Network Trace

In the Wireshark trace taken below, the AIM Manager is on and the Microsoft DHCP Server is on
Download Wireshark Trace

Routing Information Page

From AIM version 4.6 onwards, a page has been added that shows you the routing table on the AIM. This is useful when implementing classless static routes to ensure that the AIM has read them from the DHCP Server and configured itself.

The page is not available from a regular link on the AIM's web interface. You need to access it directly by using the following URL:

http://<IPADDRESS>/admin/ip_routes.php where <IPADDRESS> is the IP address of the AIM Manager.

For example:

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Page last modified on Monday July 20, 2020 11:23:13 GMT-0000