suppress_frag_ndisc

file: /proc/sys/net/ipv6/conf/interface/suppress_frag_ndisc
variable: net.ipv6.conf.interface.suppress_frag_ndisc
Official reference

Control RFC 6980 (Security Implications of IPv6 Fragmentation with IPv6 Neighbor Discovery) behavior: 1 - (default) discard fragmented neighbor discovery packets 0 - allow fragmented neighbor discovery packets

Nb: per interface setting (where “interface” is the name of your network interface); “all” is a special interface: changes the settings for all interfaces.

source