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+# VPP SPAN implementation
+
+This is a memo intended to contain documentation of the VPP SPAN implementation.
+Everything that is not directly obvious should come here.
+
+
+## Switched Port Analyzer (SPAN)
+Port mirroring is used on a network switch to send a copy of network packets seen on one switch port to a network monitoring connection on another switch port.
+Can be used by network engineers or administrators to measure performnce, analyze and debug data or diagnose errors on a network.
+
+### RX traffic node
+There is one static node to mirror incomming packets.
+* span-input: Creates a copy of incomming buffer due to incomming buffers can be reused internally.
+
+Chaining: dpdk-input -> span-input ->
+* original buffer is sent to ethernet-input for processing
+* buffer copy is sent to interface-output
+
+### Configuration
+SPAN supports the following CLI configuration commands:
+
+#### Enable/Disable SPAN (CLI)
+	set interface span <if-name> [disable | destination <if-name>]
+
+<if-name>: mirrored interface name
+destination <if-name>: monitoring interface name
+disable: delete mirroring
+
+#### Enable/Disabl SPAN (API)
+SPAN supports the following API configuration command:
+	sw_interface_span_enable_disable src GigabitEthernet0/8/0 dst GigabitEthernet0/9/0
+	sw_interface_span_enable_disable src_sw_if_index 1 dst_sw_if_index 2
+
+src/src_sw_if_index: mirrored interface name
+dst/dst_sw_if_index: monitoring interface name
+
+#### Remove SPAN entry (API)
+SPAN supports the following API configuration command:
+	sw_interface_span_enable_disable src_sw_if_index 1 dst_sw_if_index 2 disable
+
+src_sw_if_index: mirrored interface name
+dst_sw_if_index: monitoring interface name
+
+### Configuration example
+
+Mirror all packets on interface GigabitEthernet0/10/0 to interface GigabitEthernet0/11/0.
+
+Configure IPv4 addresses on mirrored interface:
+set interface ip address GigabitEthernet0/10/0 192.168.1.13/24
+set interface state GigabitEthernet0/10/0 up
+
+Configure IPv4 addresses on monitoring interface:
+set interface ip address GigabitEthernet0/11/0 192.168.2.13/24
+set interface state GigabitEthernet0/11/0 up
+
+Configure SPAN
+set span src GigabitEthernet0/10/0 dst GigabitEthernet0/11/0
+
+### Operational data
+
+Active SPAN mirroring CLI show command:
+    show interfaces span
+
+Active SPAN mirroring API dump command:
+    sw_interface_span_dump