Reference Manual

NAME

seti - set the NDIS3PKT mode and MTU for a specified inteface.

seti ifn [mode][mtu]

When invoked with only the ifn argument, seti prints the current NDIS3PKT mode (in hexadecimal) and the NAT32 Maximum Transfer Unit (in decimal) for the specified interface. Argument ifn can also be the value p to denote the Primary Interface.

The NDIS3PKT mode value is normally determined automatically, but it must be set manually if an interface uses the PPPoE protocol. The possible values for mode are:

32768    LAN adapter
32776    WAN adapter
-1       PPPoE adapter (normal mode)
-2       PPPoE adapter (special mode)

Argument mtu can specify a non-standard MTU for the specified interface. For some implementations of the PPPoE protocol, an MTU of 1400 should be specified.

The altered settings are not recorded in any netcfg file or in the Windows Registry. To make the settings permanent, the command should be placed in file startup.

Only some implementations of PPPoE require the use of this command. The mode adjustment has the effect that ARP will not be used on the specified interface. Instead, all packets will be sent to the MAC Address: 44:45:53:54:77:77 if -1 was specified, or to 44:45:53:54:61:70 if -2 was specified. Mode -2 is required for the NTSPPPOE driver running on NT (but not 95/98).

Because the Interface Configuration Dialog Box PPPoE checkbox sets mode to -1 if checked, a corrective seti p -2 1412 command may need to be issued for the above driver.

The MTU adjusment has the effect that maximum length (1500 byte) packets arriving from a private machine will be fragmented at the IP layer before being sent via the Primary Interface. This should make it unnecessary to change the MTU on all attached machines.

Note that most computers will use Path MTU Discovery to learn of non-standard MTUs on any network on the path to a packet's destination. NAT32 fully supports PMTU Discovery and will respond with an appropriate ICMP packet to notify the sender of the reduced MTU on the PPPoE Interface, again making MTU changes on the attached machines unnecessary.

mtu, netcfg, pppoe, setp