IP fragmentation is used to fragment a packet that is larger than the MTU of the egress interface, so that the packet can be transported over that interface.
For IPv4, the router fragments or discards the IP packets based on whether the DF (Do not fragment) bit is set in the IP header. If the packet that exceeds the MTU cannot be fragmented, the packet is discarded and an ICMP message ‟Fragmentation Needed and Don’t Fragment was Set” is sent back to the source IP address.
For IPv6, the router cannot fragment the packet so must discard it. An ICMP message ‟Packet too big” is sent back to the source node.
As a source of self-generated traffic, the 7705 SAR can perform packet fragmentation.
Fragmentation can be enabled for GRE tunnels. Refer to the ‟GRE Fragmentation” section in the 7705 SAR Services Guide for more information.