Draytek vigor2760 series User Manual page 193

Accept large incoming...
Enable Strict Security
Firewall
Accept routing packet
from WAN
Some on-line games (for example: Half Life) will use lots
of fragmented UDP packets to transfer game data.
Instinctively as a secure firewall, Vigor router will reject
these fragmented packets to prevent attack unless you
enable "Accept large incoming fragmented UDP or
ICMP Packets". By checking this box, you can play these
kinds of on-line games. If security concern is in higher
priority, you cannot enable "Accept large incoming
fragmented UDP or ICMP Packets".
For the sake of security, the router will execute strict
security checking for data transmission.
Such feature is enabled in default. All the packets, while
transmitting through Vigor router, will be filtered by
firewall. If the firewall system (e.g., content filter server)
does not make any response (pass or block) for these
packets, then the router's firewall will block the packets
directly.
Usually, IPv6 network sessions/traffic from WAN to LAN
will be blocked by IPv6 firewall to prevent remote client
accessing into the PCs on LAN in default.
IPv6 - Check the box to make the packets (routed from
WAN to LAN) via IPv6 being accepted by such router. It is
effective only for the packets routed but not for packets
translated by NAT.
IPv4 - Check the box to make the incoming packets via
IPv4 being accepted by such router. It is effective only for
the packets routed but not for packets translated by NAT.
177 Vigor2760 Series User's Guide