Variable Length Subnet MaskVLSM Variable Length Subnetting VLSM

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 WAN 2 WAN 1 WAN 3 Taichung 12 users Tainan 12 users Kaohsiung 28 users • 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/required addresses Taipei/60 Kaohsiung/28 Taichung/12 Tainan/12 WAN 1/2 WAN 2/2 WAN 3/2 Subnet address 192. 168. 12. 0 Address range Broadcast Address/subnet

VLSM Design Scheme Name/required addresses Taipei/60 Kaohsiung/28 Taichung/12 Tainan/12 WAN 1/2 WAN 2/2 WAN 3/2 Subnet address Address range Broadcast Address/subnet 192. 168. 12. 0 . 1 - 62 . 63 192. 168. 12. 0/26

VLSM Design Scheme Name/required addresses 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 WAN 1/2 WAN 2/2 WAN 3/2

VLSM Design Scheme Name/required addresses 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 WAN 1/2 WAN 2/2 WAN 3/2

VLSM Design Scheme Name/required addresses 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. 112/2 8 WAN 1/2 WAN 2/2 WAN 3/2

VLSM Design Scheme Name/required addresses 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. 112/2 8 WAN 1/2 192. 168. 128 . 129 -. 130 . 131 192. 168. 128/3 0 WAN 2/2 WAN 3/2

VLSM Design Scheme Name/required addresses 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. 112/2 8 WAN 1/2 192. 168. 128 . 129 -. 130 . 131 192. 168. 128/3 0 WAN 2/2 192. 168. 12. 132 . 133 - 134 . 135 192. 168. 12. 132/3 0 WAN 3/2

VLSM Design Scheme Name/required addresses 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. 112/2 8 WAN 1/2 192. 168. 128 . 129 -. 130 . 131 192. 168. 128/3 0 WAN 2/2 192. 168. 12. 132 . 133 - 134 . 135 192. 168. 12. 132/3 0 WAN 3/2 192. 168. 12. 136 . 137 -. 138 . 139 192. 168. 12. 136/3 0

Networking Scheme Taipei/3620 192. 168. 12. 0/26 S 1/0. 129 E 0/0. 1 S 1/2. 133 S 1/1. 137 WAN 1 192. 168. 128/30 S 1/. 130 F 0/. 97 Taichung/1721 192. 168. 12. 96/28 WAN 2 192. 168. 12. 132/30 WAN 3 192. 168. 12. 136/30 S 1/. 138 F 0/. 113 Tainan/1721 192. 168. 12. 112/28 S 1/. 134 F 0/. 65 Kaohsiung/1721 192. 168. 12. 64/27