There are some interoperability issues to consider when using vSphere 5.1 port mirroring with other features of vSphere.

vMotion

vMotion functions differently depending on which vSphere 5.1 port mirroring session type you select. During vMotion, a mirroring path could be temporarily invalid, but is restored when vMotion completes.

Table 1. vMotion Interoperability with port mirroring
Port mirroring session type Source and destination Interoperable with vMotion Functionality
Distributed Port Mirroring Non-uplink distributed port source and destination Yes Port mirroring between distributed ports can only be local. If the source and destination are on different hosts due to vMotion, mirroring between them will not work. However, if the source and destination move to the same host, port mirroring works.
Remote Mirroring Source Non-uplink distributed port source Yes When a source distributed port is moved from host A to host B, the original mirroring path from the source port to A's uplink is removed on A, and a new mirroring path from the source port to B's uplink is created on B. Which uplink is used is determined by the uplink name specified in session.
Uplink port destinations No Uplinks can not be moved by vMotion.
Remote Mirroring Destination VLAN source No
Non-uplink distributed port destination Yes When a destination distributed port is moved from host A to host B, all original mirroring paths from source VLANs to the destination port are moved from A to B.
Encapsulated Remote Mirroring (L3) Source Non-uplink distributed port source Yes When a source distributed port is moved from host A to host B, all original mirroring paths from the source port to destination IPs are moved from A to B.
IP destination No
Distributed Port Mirroring (legacy) IP source No
Non-uplink distributed port destination No When a destination distributed port is moved from host A to host B, all original mirroring paths from source IPs to the destination port are invalid because the port mirroring session source still sees the destination on A.

TSO and LRO

TCP Segmentation Offload (TSO) and large receive offload (LRO) might cause the number of mirroring packets to not equal to the number of mirrored packets.

When TSO is enabled on a vNIC, the vNIC might send a large packet to a distributed switch. When LRO is enabled on a vNIC, small packets sent to it might be merged into a large packet.

Source Destination Description
TSO LRO Packets from the source vNIC might be large packets, and whether they are split is determined by whether their sizes are larger than the destination vNIC LRO limitation.
TSO Any destination Packets from the source vNIC might be large packets, and they are split to standard packets at the destination vNIC.
Any source LRO Packets from the source vNIC are standard packets, and they might be merged into larger packets at the destination vNIC.