Fundamentals of Mirroring

Local mirroring allows a device to copy traffic on an interface and export the traffic through another interface. As shown in Figure 1, port 1 is a local mirrored port and port 3 is a local observing port.

Figure 1 Networking of local port mirroring

Mirroring can be classified into the following types based on mirroring policies:

Port mirroring: All traffic sent and received by a port is mirrored.
Flow mirroring: Traffic is mirrored only when it matches a configured filter rule.

Supported Local Mirroring Features

Mirrors data that is sent or received by a physical port.
- Mirrors packets received by a mirrored port and sends the packets through a specified observing port.
- Mirrors packets sent by a mirrored port and sends the packets through a specified observing port.
- Packets received or sent by a mirrored port can be mirrored to either the same observing port or different observing ports.
Mirrors data that is sent or received by a VLAN sub-interface.
- Mirrors Ethernet packets only containing an outer tag equal to a specified VLAN ID and sends these packets through a specified observing port to filter packets based on their VLAN IDs.
Mirrors data based on traffic classification.
- Mirrors packets that match multi-field (MF) classification rules, such as rules with specified source IP addresses and destination IP addresses, and then sends them through a specified observing port.
Performs the CAR function for mirrored traffic.
- Sets the committed information rate (CIR) to minimize the impact of mirrored packets on regular forwarding.
Mirrors packets to be sent to the CPU.
- Mirrors only the packets that are sent to the CPU and sends the packets through a specified observing port.
Removes labels from packets on an observing port.
- Allows an observing port to remove a maximum of two labels from mirrored packets. This function is supported only by main ports that function as observing ports.
Configures whether a mirrored packet carries a Layer 2 header in local mirroring.
- Allows a sub-interface functioning as an observing port to remove the Layer 2 header from an original packet. Then the observing port sends packets merely carrying Layer 1 and Layer 2 headers.
Supports packet mirroring filter rules.
- Supports filter rule configurations and filters packets based on filter rules.
Mirrors packet content based on a specified length.
- Sets a length for packet content to be mirrored.