the normal mtu (maximum transmit unit) value for most ethernet networks is 1500 bytes. for some isps, particularly some using pppoe, you may need to reduce the mtu. this is rarely required, and should not be done unless you are sure it is necessary for your isp connection.

    any packets sent through the firewall that are larger than the configured mtu size will be repackaged into smaller packets to meet the mtu requirement. to change the mtu size:

    1.under mtu size, select custom.

    2.enter a new size between 64 and 1500.

    3.click apply to save the new configuration.