HP-UX LAN Administrator's Guide (Feburary 2007)

Network AddressingDRAFT COPY
Variable-Length Subnet Addressing
Chapter 7122
If hosts are added to subnet B above, so that all of its remaining “g” bits become “h” bits, the
mask in subnet B also must change. Table 7-9 shows the results of these changes. Also, two
additional subnets have been added, subnet E and subnet F.
Notice that these additions caused A to change its leftmost g-bit into a subnet-bit (“s” bit).
With the addition of subnet address 101 for subnet E, the old subnet address 10 of subnet A
must be changed to 100 so that the proper number of bits are used to make the subnet
numbers unique.
Table 7-10 shows the results of removing subnet E.
Notice that with this change, subnet A gains back one growth bit (“g” bit) as its old subnet
address of 10 is now unique again.
Table 7-9 Subnets with Subnet Mask (B) Modified
Subnet
Host Address
(Bits)
Subnet Mask
(Bits)
A 100g gghh 1111 1000
B 01hh hhhh 1100 0000
C 110g ghhh 1111 1000
D 001g ghhh 1111 1000
E 101g ghhh 1111 1000
F 1110 ghhh 1111 1000
Table 7-10 Subnets with Subnet E Removed
Subnet
Host Address
(Bits)
Subnet Mask
(Bits)
A 10gg gghh 1111 1100
B 01hh hhhh 1100 0000
C 110g ghhh 1111 1000
D 001g ghhh 1111 1000
F 1110 ghhh 1111 1000