Packet mirroring allows you to collect packets on specified ports and then send them to another port to be collected and analyzed. All FortiSwitch models support switched port analyzer (SPAN) mode, which mirrors traffic to the specified destination interface without encapsulation.
Using remote SPAN (RSPAN) or encapsulated RSPAN (ERSPAN) allows you to send the collected packets across layer-2 domains. You can have multiple RSPAN sessions but only one ERSPAN session. In RSPAN mode, traffic is encapsulated in a VLAN. In ERSPAN mode, traffic is encapsulated in Ethernet, IPv4, and generic routing encapsulation (GRE) headers.
- Mirror sources cannot also be mirror destinations or members of mirror destinations if the destination is a trunk. When using RSPAN or ERSPAN in FortiLink mode, the destination ports or trunks are determined automatically (the automatically determined port can be viewed with the
diagnose switch-controller switch-info mirror statuscommand on the FortiGate device). The destination is often an ISL interface towards the FortiGate device. This destination can cause conflicts if the user tries to configure ports in the ISL as source ports. In the case of conflict, Fortinet recommends disabling the FortiLink traffic sniffer or omitting ports that are part of the ISL.
- Some models support setting the mirror destination to “internal.” This is intended only for debugging purposes and might prevent critical protocols from operating on ports being used as mirror sources.
- When there are multiple mirror sessions in the FS-108D-POE, FS-224D-POE, and FSR-112D-POE models, some traffic might not be mirrored to the destination ports.
- Some destination ports are not listed because those models (FSR-112D-POE, FS-108E, FS-124E, FS-108E-POE, FS-108E-FPOE, FS-124E-POE, FS-124E-FPOE, FS-148E, FS-148E-POE, FS-108F, FS-108F-POE, FS-108F-FPOE, FS-124F, FS-124F-POE, FS-124F-FPOE, FS-148F, FS-148F-POE, and FS-148F-FPOE) do not support mirroring to the software interface.
- You cannot select a destination interface for the ERSPAN auto mirror.
- In cases where the mirrored traffic is not unicast, or is flooded unicast, and the mirrored and non-mirrored packets both leave the mirror “dst” port, the
mirror-qosvalue is overridden by the QoS value of the non-mirrored packet.
- You can use the following commands to specify the quality of service (QoS) priority for mirrored packets on the FortiSwitch unit doing the mirroring:
config switch global
set mirror-qos <0-7>
Some of the platform differences are listed in the following table:
This section covers the following topics: