A method of monitoring a packet, which is applied in a Software Defined Network, SDN, wherein the SDN includes a controller, routers (R10, R20), Virtual Extensible Local Area Network, VXLAN, Tunnel End Points, VTEPs (101, 102, 103, 104), and hosts (210-240, 21), the method comprising: receiving, by a VTEP of the VTEPs (101, 102, 103, 104), a packet; in case that the packet is a user packet which is received through a user-side port on the VTEP and from a local monitored host, performing, by the VTEP, the following operations according to a first forwarding entry matching with the packet in a local forwarding table: mirroring, by the VTEP, the packet to obtain a mirror packet, performing, by the VTEP, a VXLAN encapsulation for the mirror packet with an identifier of a monitoring server to obtain a VXLAN packet, and sending, by the VTEP, the VXLAN packet to a remote VTEP accessed by the monitoring server, or sending the mirror packet to the monitoring server which locally accesses the VTEP; in case that the packet is a user packet which is received through a user-side port on the VTEP and is to be sent from a local host to a remote monitored host, performing, by the VTEP, the following operations according to a second forwarding entry matching with the packet in the local forwarding table: mirroring, by the VTEP, the packet to obtain a mirror packet, performing, by the VTEP, a VXLAN encapsulation for the mirror packet with an identifier of a monitoring server to obtain a VXLAN packet, and sending, by the VTEP, the VXLAN packet to a remote VTEP accessed by the monitoring server, or sending, by the VTEP, the mirror packet to the monitoring server which locally accesses the VTEP; and in case that the packet is a VXLAN packet received through a public-network-side port on the VTEP, wherein the VXLAN packet comes from a remote VTEP and carries an identifier of a monitoring server, performing, by the VTEP, the following operations according to a third forwarding entry matching the packet in the local forwarding table: de-encapsulating, by the VTEP, the VXLAN packet to obtain a packet, and sending, by the VTEP, the obtained packet to the monitoring server which locally accesses the VTEP, wherein each of the first forwarding entry, the second forwarding entry and the third forwarding entry has a match rule for a packet and an action to be performed when the packet meets the match rule. receiving, by a VTEP of the VTEPs (101, 102, 103, 104), a packet; in case that the packet is a user packet which is received through a user-side port on the VTEP and from a local monitored host, performing, by the VTEP, the following operations according to a first forwarding entry matching with the packet in a local forwarding table: mirroring, by the VTEP, the packet to obtain a mirror packet, performing, by the VTEP, a VXLAN encapsulation for the mirror packet with an identifier of a monitoring server to obtain a VXLAN packet, and sending, by the VTEP, the VXLAN packet to a remote VTEP accessed by the monitoring server, or sending the mirror packet to the monitoring server which locally accesses the VTEP; mirroring, by the VTEP, the packet to obtain a mirror packet, performing, by the VTEP, a VXLAN encapsulation for the mirror packet with an identifier of a monitoring server to obtain a VXLAN packet, and sending, by the VTEP, the VXLAN packet to a remote VTEP accessed by the monitoring server, or sending the mirror packet to the monitoring server which locally accesses the VTEP; in case that the packet is a user packet which is received through a user-side port on the VTEP and is to be sent from a local host to a remote monitored host, performing, by the VTEP, the following operations according to a second forwarding entry matching with the packet in the local forwarding table: mirroring, by the VTEP, the packet to obtain a mirror packet, performing, by the VTEP, a VXLAN encapsulation for the mirror packet with an identifier of a monitoring server to obtain a VXLAN packet, and sending, by the VTEP, the VXLAN packet to a remote VTEP accessed by the monitoring server, or sending, by the VTEP, the mirror packet to the monitoring server which locally accesses the VTEP; and mirroring, by the VTEP, the packet to obtain a mirror packet, performing, by the VTEP, a VXLAN encapsulation for the mirror packet with an identifier of a monitoring server to obtain a VXLAN packet, and sending, by the VTEP, the VXLAN packet to a remote VTEP accessed by the monitoring server, or sending, by the VTEP, the mirror packet to the monitoring server which locally accesses the VTEP; and in case that the packet is a VXLAN packet received through a public-network-side port on the VTEP, wherein the VXLAN packet comes from a remote VTEP and carries an identifier of a monitoring server, performing, by the VTEP, the following operations according to a third forwarding entry matching the packet in the local forwarding table: de-encapsulating, by the VTEP, the VXLAN packet to obtain a packet, and sending, by the VTEP, the obtained packet to the monitoring server which locally accesses the VTEP, de-encapsulating, by the VTEP, the VXLAN packet to obtain a packet, and sending, by the VTEP, the obtained packet to the monitoring server which locally accesses the VTEP, wherein each of the first forwarding entry, the second forwarding entry and the third forwarding entry has a match rule for a packet and an action to be performed when the packet meets the match rule.