IPRangeExplorer

129.0.0.0/17

Public

Class B — /17 prefix — 32,766 usable hosts

Network Address
129.0.0.0
Broadcast Address
129.0.127.255
Subnet Mask
255.255.128.0
Usable Hosts
32,766
First Usable IP
129.0.0.1
Last Usable IP
129.0.127.254
Total IPs
32,768
Prefix Length
/17

Network address — the base address of the block (129.0.0.0). All devices in this subnet share this prefix. Cannot be assigned to a host.

Broadcast address — packets sent to 129.0.127.255 are delivered to every device in the subnet. Also reserved — not assignable.

Usable hosts — the 32,766 addresses between those two that you can assign to servers, VMs, or interfaces.

Subnet mask — 255.255.128.0 is the dotted-decimal equivalent of /17. Older tools and Cisco configs use this format instead of CIDR slash notation.

Full Details

CIDR Notation 129.0.0.0/17
Network Address 129.0.0.0
Broadcast Address 129.0.127.255
Subnet Mask 255.255.128.0
Wildcard Mask 0.0.127.255
Prefix Length /17
IP Address Class Class B
Total IP Addresses 32,768
Usable Host Addresses 32,766
First Usable IP 129.0.0.1
Last Usable IP 129.0.127.254
Network (Hex) 0x81000000
Broadcast (Hex) 0x81007FFF
Address Type Public / Globally Routable

Binary Representation

Network Address
10000001.00000000 10000001.00000000.00000000.00000000
Subnet Mask
11111111.11111111.10000000.00000000

The first 17 bits (1s in the mask) identify the network. The remaining 15 bits identify hosts within the network.

Split into Equal Subnets

Split 129.0.0.0/17 into 2 equal /18 subnets (16,382 usable hosts each).

# CIDR Network First Usable Last Usable Broadcast Hosts
1 129.0.0.0/18 129.0.0.0 129.0.0.1 129.0.63.254 129.0.63.255 16,382
2 129.0.64.0/18 129.0.64.0 129.0.64.1 129.0.127.254 129.0.127.255 16,382

/17 Subnet Reference

Total IPs 32,768
Usable Hosts 32,766
Subnet Mask 255.255.128.0
Wildcard 0.0.127.255
Full /17 reference →

Related Ranges

Parent /16 block 129.0.0.0/16 Sibling /17 block 129.0.128.0/17

Adjacent Prefix Sizes

/15 131,070 hosts /16 65,534 hosts /17 32,766 hosts /18 16,382 hosts /19 8,190 hosts

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