Virtual Private Port Service (VPPS) MTU Handling and Remote Mirroring

You must assure that a jumbo path exists between the two tunnel endpoints. When packets enter a VPPS, packet size increases by the size of the extra layer 3 IP and the GRE headers. This packet size increase can range from 38 to 64 bytes, depending upon IP and GRE configuration. If an encapsulated packet exceeds the destination MTU, the packet is dropped. ICMP does not report back to the source that the packet exceeded MTU for a tunnel with mirroring enabled. A VPPS will report back to the original source. Jumbo Frames for Jumbo port configuration details.