TP-Link TD-8840T User Manual page 27

Click Advanced, advanced selections for WAN Service Setup can be shown.
MTU (bytes): Maximum Transmission Unit Size. Check this box then you can change the MTU
size. The default MTU value is 1500 Bytes. It is not recommended that you change the default
value unless required by your ISP.
Enable NAT: This technology translates the IP addresses of a local area network to a different
IP address for the Internet. If this Modem Router is hosting your network's connection to the
Internet, please select the check box. If another Router exists in your network, you don't need
to select the option.
Enable Fullcone NAT: It is a type of NAT, if not enabled, the default NAT will act.
Enable SPI Firewall: A SPI firewall enhances network's security. Select the option to use a
firewall, or else without a firewall.
Enable IGMP Proxy: IGMP (Internet Group Management Protocol) is used to manage
multicasting on TCP/IP networks. Some ISPs use IGMP to perform remote configuration for
client devices, such as the Modem Router. The default value is disabled, and if you are not
sure, please contact your ISP or just leave it.
Get IP Unicast: This is disabled by default. The minority of DHCP Server of ISP will not
support to enable this. When the Route is connected right but IP cannot get, you can select
this box.
TD-8840T ADSL2+ Modem Router User Guide
Figure 4-5
21