21.64.0.0/13

Public

Class A — /13 prefix — 524,286 usable hosts

Network Address

21.64.0.0

Broadcast Address

21.71.255.255

Subnet Mask

255.248.0.0

Usable Hosts

524,286

First Usable IP

21.64.0.1

Last Usable IP

21.71.255.254

Total IPs

524,288

Prefix Length

/13

Network address — the base address of the block (21.64.0.0). All devices in this subnet share this prefix. Cannot be assigned to a host.

Broadcast address — packets sent to 21.71.255.255 are delivered to every device in the subnet. Also reserved — not assignable.

Usable hosts — the 524,286 addresses between those two that you can assign to servers, VMs, or interfaces.

Subnet mask — 255.248.0.0 is the dotted-decimal equivalent of /13. Older tools and Cisco configs use this format instead of CIDR slash notation.

Full Details

CIDR Notation	21.64.0.0/13
Network Address	21.64.0.0
Broadcast Address	21.71.255.255
Subnet Mask	255.248.0.0
Wildcard Mask	0.7.255.255
Prefix Length	/13
IP Address Class	Class A
Total IP Addresses	524,288
Usable Host Addresses	524,286
First Usable IP	21.64.0.1
Last Usable IP	21.71.255.254
Network (Hex)	0x15400000
Broadcast (Hex)	0x1547FFFF
Address Type	Public / Globally Routable

Binary Representation

Network Address

00010101 00010101.01000000.00000000.00000000

Subnet Mask

11111111.11111000.00000000.00000000

The first 13 bits (1s in the mask) identify the network. The remaining 19 bits identify hosts within the network.

Split into Equal Subnets

Split 21.64.0.0/13 into 2 equal /14 subnets (262,142 usable hosts each).

#	CIDR	Network	First Usable	Last Usable	Broadcast	Hosts
1	21.64.0.0/14	21.64.0.0	21.64.0.1	21.67.255.254	21.67.255.255	262,142
2	21.68.0.0/14	21.68.0.0	21.68.0.1	21.71.255.254	21.71.255.255	262,142

Split 21.64.0.0/13 into 4 equal /15 subnets (131,070 usable hosts each).

#	CIDR	Network	First Usable	Last Usable	Broadcast	Hosts
1	21.64.0.0/15	21.64.0.0	21.64.0.1	21.65.255.254	21.65.255.255	131,070
2	21.66.0.0/15	21.66.0.0	21.66.0.1	21.67.255.254	21.67.255.255	131,070
3	21.68.0.0/15	21.68.0.0	21.68.0.1	21.69.255.254	21.69.255.255	131,070
4	21.70.0.0/15	21.70.0.0	21.70.0.1	21.71.255.254	21.71.255.255	131,070

Split 21.64.0.0/13 into 8 equal /16 subnets (65,534 usable hosts each).

#	CIDR	Network	First Usable	Last Usable	Broadcast	Hosts
1	21.64.0.0/16	21.64.0.0	21.64.0.1	21.64.255.254	21.64.255.255	65,534
2	21.65.0.0/16	21.65.0.0	21.65.0.1	21.65.255.254	21.65.255.255	65,534
3	21.66.0.0/16	21.66.0.0	21.66.0.1	21.66.255.254	21.66.255.255	65,534
4	21.67.0.0/16	21.67.0.0	21.67.0.1	21.67.255.254	21.67.255.255	65,534
5	21.68.0.0/16	21.68.0.0	21.68.0.1	21.68.255.254	21.68.255.255	65,534
6	21.69.0.0/16	21.69.0.0	21.69.0.1	21.69.255.254	21.69.255.255	65,534
7	21.70.0.0/16	21.70.0.0	21.70.0.1	21.70.255.254	21.70.255.255	65,534
8	21.71.0.0/16	21.71.0.0	21.71.0.1	21.71.255.254	21.71.255.255	65,534

Split 21.64.0.0/13 into 16 equal /17 subnets (32,766 usable hosts each).

#	CIDR	Network	First Usable	Last Usable	Broadcast	Hosts
1	21.64.0.0/17	21.64.0.0	21.64.0.1	21.64.127.254	21.64.127.255	32,766
2	21.64.128.0/17	21.64.128.0	21.64.128.1	21.64.255.254	21.64.255.255	32,766
3	21.65.0.0/17	21.65.0.0	21.65.0.1	21.65.127.254	21.65.127.255	32,766
4	21.65.128.0/17	21.65.128.0	21.65.128.1	21.65.255.254	21.65.255.255	32,766
5	21.66.0.0/17	21.66.0.0	21.66.0.1	21.66.127.254	21.66.127.255	32,766
6	21.66.128.0/17	21.66.128.0	21.66.128.1	21.66.255.254	21.66.255.255	32,766
7	21.67.0.0/17	21.67.0.0	21.67.0.1	21.67.127.254	21.67.127.255	32,766
8	21.67.128.0/17	21.67.128.0	21.67.128.1	21.67.255.254	21.67.255.255	32,766
9	21.68.0.0/17	21.68.0.0	21.68.0.1	21.68.127.254	21.68.127.255	32,766
10	21.68.128.0/17	21.68.128.0	21.68.128.1	21.68.255.254	21.68.255.255	32,766
11	21.69.0.0/17	21.69.0.0	21.69.0.1	21.69.127.254	21.69.127.255	32,766
12	21.69.128.0/17	21.69.128.0	21.69.128.1	21.69.255.254	21.69.255.255	32,766
13	21.70.0.0/17	21.70.0.0	21.70.0.1	21.70.127.254	21.70.127.255	32,766
14	21.70.128.0/17	21.70.128.0	21.70.128.1	21.70.255.254	21.70.255.255	32,766
15	21.71.0.0/17	21.71.0.0	21.71.0.1	21.71.127.254	21.71.127.255	32,766
16	21.71.128.0/17	21.71.128.0	21.71.128.1	21.71.255.254	21.71.255.255	32,766

/13 Subnet Reference

Total IPs 524,288

Usable Hosts 524,286

Subnet Mask 255.248.0.0

Wildcard 0.7.255.255

Full /13 reference →

Related Ranges

Parent /12 block 21.64.0.0/12 Sibling /13 block 21.72.0.0/13

Adjacent Prefix Sizes

/11 2,097,150 hosts /12 1,048,574 hosts /13 524,286 hosts /14 262,142 hosts /15 131,070 hosts