172.16.0.0/12
1️⃣ Netmask
Prefix /12 berarti ada 12 bit untuk network.
Biner netmask:
11111111.11110000.00000000.00000000
Desimalnya adalah:
➡️ 255.240.0.0
2️⃣ Blok Subnet (Subnet Increment)
Lihat oktet yang “kena potong” terakhir di netmask:
255.240.0.0 → angka 240 ada di oktet ke-2
Rumus blok = 256 − 240 = 16
➡️ Blok subnet = kelipatan 16 pada oktet ke-2
Jadi subnet akan mulai dari:
172.16.x.x
172.32.x.x
172.48.x.x
172.64.x.x
...
sampai sebelum 172.32+16 berulang terus
3️⃣ Jumlah Subnet
Alamat 172.x.x.x adalah Class B
Default Class B = /16
Sekarang dipakai /12, artinya lebih besar dari default (supernetting).
Selisih bit:
/16 → /12 = mundur 4 bit
Jumlah subnet (dibanding classful)
[
2^{4} = 16 subnet
]
➡️ Jumlah subnet = 16
4️⃣ Jumlah Host Keseluruhan (per subnet)
Sisa bit host:
32 − 12 = 20 bit host
Total IP per subnet:
[
2^{20} = 1.048.576 alamat IP
]
➡️ Jumlah host keseluruhan = 1.048.576 IP
5️⃣ Jumlah Host Valid
Kurangi network & broadcast:
[
1.048.576 - 2 = 1.048.574
]
➡️ Host valid per subnet = 1.048.574 IP
6️⃣ Detail IP Address Tiap Subnet
Karena bloknya 16 di oktet ke-2, maka subnetnya:
Subnet Network Address IP Pertama IP Terakhir Broadcast
1 172.16.0.0/12 172.16.0.1 172.31.255.254 172.31.255.255
2 172.32.0.0/12 172.32.0.1 172.47.255.254 172.47.255.255
3 172.48.0.0/12 172.48.0.1 172.63.255.254 172.63.255.255
4 172.64.0.0/12 172.64.0.1 172.79.255.254 172.79.255.255
5 172.80.0.0/12 172.80.0.1 172.95.255.254 172.95.255.255
6 172.96.0.0/12 172.96.0.1 172.111.255.254 172.111.255.255
7 172.112.0.0/12 172.112.0.1 172.127.255.254 172.127.255.255
8 172.128.0.0/12 172.128.0.1 172.143.255.254 172.143.255.255
9 172.144.0.0/12 172.144.0.1 172.159.255.254 172.159.255.255
10 172.160.0.0/12 172.160.0.1 172.175.255.254 172.175.255.255
11 172.176.0.0/12 172.176.0.1 172.191.255.254 172.191.255.255
12 172.192.0.0/12 172.192.0.1 172.207.255.254 172.207.255.255
13 172.208.0.0/12 172.208.0.1 172.223.255.254 172.223.255.255
14 172.224.0.0/12 172.224.0.1 172.239.255.254 172.239.255.255
15 172.240.0.0/12 172.240.0.1 172.255.255.254 172.255.255.255
16 (berhenti sebelum lewat 172.x batas Class B)
🔥 Ringkasan Cepat
Item Hasil
Netmask 255.240.0.0
Blok Subnet 16 (oktet ke-2)
Jumlah Subnet 16
Host per Subnet 1.048.576
Host Valid 1.048.574