39.151.208.0/21

Public

Class A — /21 prefix — 2,046 usable hosts

Network Address

39.151.208.0

Broadcast Address

39.151.215.255

Subnet Mask

255.255.248.0

Usable Hosts

2,046

First Usable IP

39.151.208.1

Last Usable IP

39.151.215.254

Total IPs

2,048

Prefix Length

/21

Network address — the base address of the block (39.151.208.0). All devices in this subnet share this prefix. Cannot be assigned to a host.

Broadcast address — packets sent to 39.151.215.255 are delivered to every device in the subnet. Also reserved — not assignable.

Usable hosts — the 2,046 addresses between those two that you can assign to servers, VMs, or interfaces.

Subnet mask — 255.255.248.0 is the dotted-decimal equivalent of /21. Older tools and Cisco configs use this format instead of CIDR slash notation.

Full Details

CIDR Notation	39.151.208.0/21
Network Address	39.151.208.0
Broadcast Address	39.151.215.255
Subnet Mask	255.255.248.0
Wildcard Mask	0.0.7.255
Prefix Length	/21
IP Address Class	Class A
Total IP Addresses	2,048
Usable Host Addresses	2,046
First Usable IP	39.151.208.1
Last Usable IP	39.151.215.254
Network (Hex)	0x2797D000
Broadcast (Hex)	0x2797D7FF
Address Type	Public / Globally Routable

Binary Representation

Network Address

00100111.10010111 00100111.10010111.11010000.00000000

Subnet Mask

11111111.11111111.11111000.00000000

The first 21 bits (1s in the mask) identify the network. The remaining 11 bits identify hosts within the network.

Split into Equal Subnets

Split 39.151.208.0/21 into 2 equal /22 subnets (1,022 usable hosts each).

#	CIDR	Network	First Usable	Last Usable	Broadcast	Hosts
1	39.151.208.0/22	39.151.208.0	39.151.208.1	39.151.211.254	39.151.211.255	1,022
2	39.151.212.0/22	39.151.212.0	39.151.212.1	39.151.215.254	39.151.215.255	1,022

Split 39.151.208.0/21 into 4 equal /23 subnets (510 usable hosts each).

#	CIDR	Network	First Usable	Last Usable	Broadcast	Hosts
1	39.151.208.0/23	39.151.208.0	39.151.208.1	39.151.209.254	39.151.209.255	510
2	39.151.210.0/23	39.151.210.0	39.151.210.1	39.151.211.254	39.151.211.255	510
3	39.151.212.0/23	39.151.212.0	39.151.212.1	39.151.213.254	39.151.213.255	510
4	39.151.214.0/23	39.151.214.0	39.151.214.1	39.151.215.254	39.151.215.255	510

Split 39.151.208.0/21 into 8 equal /24 subnets (254 usable hosts each).

#	CIDR	Network	First Usable	Last Usable	Broadcast	Hosts
1	39.151.208.0/24	39.151.208.0	39.151.208.1	39.151.208.254	39.151.208.255	254
2	39.151.209.0/24	39.151.209.0	39.151.209.1	39.151.209.254	39.151.209.255	254
3	39.151.210.0/24	39.151.210.0	39.151.210.1	39.151.210.254	39.151.210.255	254
4	39.151.211.0/24	39.151.211.0	39.151.211.1	39.151.211.254	39.151.211.255	254
5	39.151.212.0/24	39.151.212.0	39.151.212.1	39.151.212.254	39.151.212.255	254
6	39.151.213.0/24	39.151.213.0	39.151.213.1	39.151.213.254	39.151.213.255	254
7	39.151.214.0/24	39.151.214.0	39.151.214.1	39.151.214.254	39.151.214.255	254
8	39.151.215.0/24	39.151.215.0	39.151.215.1	39.151.215.254	39.151.215.255	254

Split 39.151.208.0/21 into 16 equal /25 subnets (126 usable hosts each).

#	CIDR	Network	First Usable	Last Usable	Broadcast	Hosts
1	39.151.208.0/25	39.151.208.0	39.151.208.1	39.151.208.126	39.151.208.127	126
2	39.151.208.128/25	39.151.208.128	39.151.208.129	39.151.208.254	39.151.208.255	126
3	39.151.209.0/25	39.151.209.0	39.151.209.1	39.151.209.126	39.151.209.127	126
4	39.151.209.128/25	39.151.209.128	39.151.209.129	39.151.209.254	39.151.209.255	126
5	39.151.210.0/25	39.151.210.0	39.151.210.1	39.151.210.126	39.151.210.127	126
6	39.151.210.128/25	39.151.210.128	39.151.210.129	39.151.210.254	39.151.210.255	126
7	39.151.211.0/25	39.151.211.0	39.151.211.1	39.151.211.126	39.151.211.127	126
8	39.151.211.128/25	39.151.211.128	39.151.211.129	39.151.211.254	39.151.211.255	126
9	39.151.212.0/25	39.151.212.0	39.151.212.1	39.151.212.126	39.151.212.127	126
10	39.151.212.128/25	39.151.212.128	39.151.212.129	39.151.212.254	39.151.212.255	126
11	39.151.213.0/25	39.151.213.0	39.151.213.1	39.151.213.126	39.151.213.127	126
12	39.151.213.128/25	39.151.213.128	39.151.213.129	39.151.213.254	39.151.213.255	126
13	39.151.214.0/25	39.151.214.0	39.151.214.1	39.151.214.126	39.151.214.127	126
14	39.151.214.128/25	39.151.214.128	39.151.214.129	39.151.214.254	39.151.214.255	126
15	39.151.215.0/25	39.151.215.0	39.151.215.1	39.151.215.126	39.151.215.127	126
16	39.151.215.128/25	39.151.215.128	39.151.215.129	39.151.215.254	39.151.215.255	126

/21 Subnet Reference

Total IPs 2,048

Usable Hosts 2,046

Subnet Mask 255.255.248.0

Wildcard 0.0.7.255

Full /21 reference →

Related Ranges

Parent /20 block 39.151.208.0/20 Sibling /21 block 39.151.216.0/21

Adjacent Prefix Sizes

/19 8,190 hosts /20 4,094 hosts /21 2,046 hosts /22 1,022 hosts /23 510 hosts