Variable Length Subnet Mask(VLSM)可變長度子網路切割
王振生
Variable Length Subnetting
‣ VLSM allows us to use one class C address to design a networking scheme to meet the following requirements:
‣ Taipei 60 users‣ Kaohsiung 28 users‣ Taichung 12 users‣ Tainan 12 users‣ WAN links between each router
Networking Requirements
Taipei 60 users
Taichung 12 users Tainan 12 users Kaohsiung 28 users
WAN 1WAN 2
WAN 3
•If a /26 was used to provide 60 addresses for LANs. There are no addresses left for WAN links•Classful subnetting is very wasteful.
VLSM Design Scheme
Name/requiredaddresses
Subnet address
Address range
Broadcast
Address/subnet
Taipei/60 192.168.12.0
Kaohsiung/28
Taichung/12
Tainan/12
WAN1/2
WAN2/2
WAN3/2
VLSM Design Scheme
Name/requiredaddresses
Subnet address
Address range
Broadcast
Address/subnet
Taipei/60 192.168.12.0
.1 - 62 .63 192.168.12.0/26
Kaohsiung/28
Taichung/12
Tainan/12
WAN1/2
WAN2/2
WAN3/2
VLSM Design Scheme
Name/requiredaddresses
Subnet address
Address range
Broadcast
Address/subnet
Taipei/60 192.168.12.0 .1 - 62 .63 192.168.12.0/26
Kaohsiung/28
192.168.12.64
.65 - .94 .95 192.168.12.64/27
Taichung/12
Tainan/12
WAN1/2
WAN2/2
WAN3/2
VLSM Design Scheme
Name/requiredaddresses
Subnet address
Address range
Broadcast
Address/subnet
Taipei/60 192.168.12.0 .1 - 62 .63 192.168.12.0/26
Kaohsiung/28
192.168.12.64
.65 - .94 .95 192.168.12.64/27
Taichung/12 192.168.12.96
.97- .110 .111 192.168.12.96/28
Tainan/12
WAN1/2
WAN2/2
WAN3/2
VLSM Design Scheme
Name/requiredaddresses
Subnet address
Address range
Broadcast
Address/subnet
Taipei/60 192.168.12.0 .1 - 62 .63 192.168.12.0/26
Kaohsiung/28 192.168.12.64 .65 - .94 .95 192.168.12.64/27
Taichung/12 192.168.12.96 .97- .110 .111 192.168.12.96/28
Tainan/12 192.168.12.112
.113 - .126 .127 192.168.12.112/28
WAN1/2
WAN2/2
WAN3/2
VLSM Design Scheme
Name/requiredaddresses
Subnet address
Address range
Broadcast
Address/subnet
Taipei/60 192.168.12.0 .1 - 62 .63 192.168.12.0/26
Kaohsiung/28 192.168.12.64 .65 - .94 .95 192.168.12.64/27
Taichung/12 192.168.12.96 .97- .110 .111 192.168.12.96/28
Tainan/12 192.168.12.112
.113 - .126 .127 192.168.12.112/28
WAN1/2 192.168.12.128
.129 - .130 .131 192.168.12.128/30
WAN2/2
WAN3/2
VLSM Design Scheme
Name/requiredaddresses
Subnet address
Address range
Broadcast
Address/subnet
Taipei/60 192.168.12.0 .1 - 62 .63 192.168.12.0/26
Kaohsiung/28 192.168.12.64 .65 - .94 .95 192.168.12.64/27
Taichung/12 192.168.12.96 .97- .110 .111 192.168.12.96/28
Tainan/12 192.168.12.112
.113 - .126 .127 192.168.12.112/28
WAN1/2 192.168.12.128
.129 - .130 .131 192.168.12.128/30
WAN2/2 192.168.12.132
.133 - 134 .135 192.168.12.132/30
WAN3/2
VLSM Design Scheme
Name/requiredaddresses
Subnet address
Address range
Broadcast
Address/subnet
Taipei/60 192.168.12.0 .1 - .62 .63 192.168.12.0/26
Kaohsiung/28 192.168.12.64 .65 - .94 .95 192.168.12.64/27
Taichung/12 192.168.12.96 .97- .110 .111 192.168.12.96/28
Tainan/12 192.168.12.112
.113 - .126 .127 192.168.12.112/28
WAN1/2 192.168.12.128
.129 - .130 .131 192.168.12.128/30
WAN2/2 192.168.12.132
.133 - 134 .135 192.168.12.132/30
WAN3/2 192.168.12.136
.137 - .138 .139 192.168.12.136/30
Networking Scheme
Taipei/3620192.168.12.0/26
Taichung/1721192.168.12.96/28
Tainan/1721192.168.12.112/28
Kaohsiung/1721192.168.12.64/27
WAN 1 192.168.12.128/30
S1/0 .129
S1/.130
S1/2 .133
S1/1 .137WAN 2
192.168.12.132/30
WAN 3 192.168.12.136/30
S1/.138
F0/.65F0/.113F0/.97
E0/0 .1
S1/.134