Installing and Administering LAN/9000 Software

18
initiate the use of these enhancements.
**A scaling factor of 1 (same as no scaling) is used unless the application
has a receive buffer greater than 2**16. Refer to the "Scaled Windows"
section below for more information.
IP Subnet Mask
The ifconfig subnet mask default now allows all 1s or all 0s in the
masked part of the subnet field. This provides up to twice as many IP
addresses as before.
The subnet field (the portion of an IP address that identifies the subnet
beyond the network portion of the address) can now be all 0's or all 1's, as
described in RFC 1878. For example, a class A IP address used with the
mask 255.192.0.0 (0xffc000000) has a two-bit subnet field:
ifconfig can now assign the following IP address and subnet mask to an
interface, although the subnet field (subnet portion of the address) is all
ones:
IP address: 15.192.1.1
Subnet mask: 255.192.0.0 (0xffc00000)
In binary:
00001111 11 000000 00000001 00000001
11111111 11 000000 00000000 00000000
ifconfig can now also assign the following IP address and subnet mask to
an interface, although the subnet field is all zeroes:
IP address: 15.1.1.1
Subnet mask: 255.192.0.0 (0xffc00000)
In binary:
00001111 00 000001 00000001 00000001
11111111 11 000000 00000000 00000000
To disallow subnet fields with all ones or all zeroes (revert to RFC 1122
behavior), set the ndd parameter ip_check_subnet_addr to 1 in the
nddconf file (/etc/rc.config.d/nddconf).
IP PMTU Discovery
Example: 11111111 11 000000 00000000 00000000
^^
subnet field