Mirror Port, TAP and Packet Broker Installation

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This section describes the installation for network situations where the Allegro Network Multimeter receives traffic. It is referred to here as Mirror Port Installation or Mirror Port Mode but it is also applicable for Tap and Packet Broker installations.

The Mirror Port is a feature that is available on almost all manageable Ethernet switches.



The Mirror Port Mode depends on the quality of the Switch mirroring. Please check the Mirror Port statistics of your Switch if all packets have been forwarded. Allegro Network Multimeter measurements depend on accurate packet mirroring and may lead to incorrect statistics if the Mirror Port is not working as expected.

Allegro recommends a separate Tap or a Packet Broker if the quality of the Mirror Port cannot be guaranteed.

What is the Mirror Port Mode?

The Allegro Network Multimeter works in the Mirror Port Mode as a traffic receiving device. It will NOT forward any traffic on the measurement Ethernet ports.

How should the Mirror Port Mode be used?

The data plane ports of the Allegro Network Multimeter should be connected in Mirror Port Mode to one or multiple Mirror Ports on a Switch. The Allegro Network Multimeter management port needs to be connected to a standard Switch port or to an out-of-band management Switch.

See #Limitations for more details.

How do I configure the Mirror Port Mode?

Please refer to your Switch manual how to set up a Switch port as a mirror port.

The Allegro Mirror Port Mode can be configured at SettingsGlobal settingsPacket processing mode. The interfaces can be configured to Bridge mode or Sink mode. The Sink mode will disable packet forwarding and transmission on the Ethernet ports. Please switch to Sink mode and save the settings at the bottom of the page Sink mode.png

Allegro Network Multimeter Data Plane Ports

Devices with built-in network ports

The Allegro 200, 500, 800, 1000, 1200, 3000, 3200, x310 and x410 series have built-in physical network ports.

Device Picture Number of Monitoring Ports Remarks
Allegro 200 Allegro-200 back cut.jpg 2
Allegro 500 Allegro-500 back cut.jpg
Allegro-500 front cut.jpg
Allegro 800-P
Allegro 800-RM
Allegro 1000
Allegro 3000
Allegro-1000 front cut.jpg 7 Can be extended by expansion cards.
Allegro 1200
Allegro 3200
Allegro-1200-front cut.jpg 7 Can be extended by expansion cards.
Allegro x210
Allegro x300
Allegro x400
Allegro x500
Allegro x510
none The Allegro x210, x300, x400, x500 and x510 series do not have built-in network ports, see section expansion cards below.
Allegro x310
Allegro x410
2 Can be extended by expansion cards.

Devices with port expansion cards

All Allegro Network Multimeters with network card expansion slots support the Mirror Port Mode. All expansion cards have either 2 or 4 network ports.

Bypass expansion cards

The Allegro Network Multimeter bypass cards deliver a fail-over when the software bypass is not active in Bridge Mode ( see In-Line installation for more details ). The bypass is deactivated when the Mirror Port Mode / Sink Mode is active.

Grouping of multiple links ( Trunk vs. separate links )

By default, the Allegro Network Multimeter processes all incoming traffic as one big pipe and it does not use the port as an criteria to separate links. If you have connected separate links at the Allegro Network Multimeter, please use the virtual link grouping feature to specify which ports belong together.

This feature can also be used to forward multiple links with a Packet Broker to one Allegro port with VLANs as a separator.

Advanced VLAN handling

Some Switches remove the VLAN for one flow direction and keep it for the other when mirroring a VLAN trunk. Usually the Allegro Network Multimeter treats different packets of different VLANs as different links. The Allegro Network Multimeter can be configured to ignore the VLAN tag. This can be done at: SettingsGlobal settingsExpert settingsVLAN handling. Do not forget to save the settings at the bottom of the page!

Ignore vlan key.png


Switch limitations

Please be aware that the Allegro Network Multimeter can only analyze packets that have been forwarded by the Switch port. Please also be aware that the exact packet timing and ordering depends on the Switch implementation. Allegro recommends the installation of a Tap to prevent any Switch side effects.