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● network/21 = Mask 255.255.248.0 • 2,046 Usable Hosts

/21 Subnet Mask (255.255.248.0): Usable Hosts (2,046), Wildcard & IPv4 Range

Instant /21 CIDR reference: Subnet Mask is 255.255.248.0, Wildcard 0.0.7.255, Total IPs 2,048, and 2,046 Usable Hosts. Ideal for ISP PPPoE Subscriber Pool & CGNAT (2,046 Hosts).

⚡ Instant Calculated Answer
/21 = Mask 255.255.248.0 • 2,046 Usable Hosts
⚡Open Full Interactive Calculator (subnet-calculator) →

📊Reference Table & Engineering Specs

Parameter / MetricSpecification Value
CIDR Prefix Notation/21
Dotted-Decimal Subnet Mask255.255.248.0
Wildcard Mask (OSPF / ACL)0.0.7.255
Total IPv4 Addresses (2^11)2,048 IP
Total Usable Hosts (2^11 - 2)2,046 Host
Sample Network ID10.10.0.0/21
Sample Usable Host Range10.10.0.1 – 10.10.7.254
Sample Broadcast Address10.10.7.255
Ideal Field Use CaseDistribusi Pelanggan PPPoE ISP & CGNAT (2.046 Host)

📖Technical Explanation & Methodology

CIDR prefix /21 allocates 21 network bits and leaves 11 host bits (32 - 21 = 11). Using 2^11, each /21 block contains 2,048 total IPs and 2,046 usable host addresses (ISP PPPoE Subscriber Pool & CGNAT (2,046 Hosts)).

💻 Ready-to-Deploy CLI Snippet:
/ip address add address=10.10.0.1/21 interface=bridge-lan comment="Subnet /21 (2046 Host) - KalkuNet.com"

❓Frequently Asked Questions (FAQ)

What is the Subnet Mask for /21?

The dotted-decimal Subnet Mask for /21 is 255.255.248.0 with a Wildcard Mask of 0.0.7.255.

How many usable hosts are in a /21 network?

A /21 subnet provides 2,048 total IPs and 2,046 usable hosts.

🔗Other Related Scenarios

/32 = Mask 255.255.255.255 • 1 Usable Hosts
/32 Subnet Mask (255.255.255.255): Usable Hosts (1), Wildcard & IPv4 Range
/30 = Mask 255.255.255.252 • 2 Usable Hosts
/30 Subnet Mask (255.255.255.252): Usable Hosts (2), Wildcard & IPv4 Range
/29 = Mask 255.255.255.248 • 6 Usable Hosts
/29 Subnet Mask (255.255.255.248): Usable Hosts (6), Wildcard & IPv4 Range
/28 = Mask 255.255.255.240 • 14 Usable Hosts
/28 Subnet Mask (255.255.255.240): Usable Hosts (14), Wildcard & IPv4 Range