/29 Subnet Calculator

A /29 subnet mask (255.255.255.248) is the standard allocation unit provided by commercial Internet Service Providers (ISPs) for small business static

Networking

Formula & Methodology

ext{Subnet Mask} = 255.255.255.248 quad ( ext{Prefix } /29) ext{Total Addresses} = 2^{32 - 29} = 2^3 = 8 ext{Usable Hosts} = 8 - 2 = 6 ext{Wildcard Mask} = 0.0.0.7

A /29 prefix reserves 29 bits for the network and leaves 3 bits for hosts. With 3 host bits, there are 2³ = 8 total IP addresses. The first address is reserved as the network identifier, and the eighth address is reserved as the broadcast address, leaving exactly 6 usable static host IPs.

Block Details for 192.168.10.0/29

6 Usable Hosts (8 Total IPs)

Overview

A /29 subnet mask (255.255.255.248) is the standard allocation unit provided by commercial Internet Service Providers (ISPs) for small business static IP blocks, DMZ firewall segments, and redundant gateway configurations. The /29 Subnet Calculator maps out the exact 8-address block for any /29 network, identifying the 6 usable host addresses, network identifier, broadcast address, and recommended default gateway.

Because public IPv4 address space is strictly limited and costly, understanding how to allocate every single usable address in a /29 block is essential for network administrators. This calculator eliminates calculation errors and provides an exact, ready-to-deploy IP assignment plan.

Worked Examples

Example 1: Public ISP Block Allocation (192.168.10.0/29)

Network Base = 192.168.10.0, Gateway = First Usable (.1)

Total addresses in /29 block: 8 (from .0 to .7).
Network ID: 192.168.10.0.
Broadcast address: 192.168.10.7.
Designated Default Gateway: 192.168.10.1.
Remaining 5 client host IPs: 192.168.10.2, .3, .4, .5, .6.

Final Answer: 6 Usable Hosts (192.168.10.1 - 192.168.10.6, Gateway: .1)

Example 2: Commercial Web Server DMZ (10.1.1.24/29)

Host IP = 10.1.1.24/29

24 is an exact multiple of 8: block spans 10.1.1.24 to 10.1.1.31.
Network address: 10.1.1.24.
Broadcast address: 10.1.1.31.
Usable hosts: 10.1.1.25 through 10.1.1.30.

Final Answer: 6 Usable Hosts (10.1.1.25 - 10.1.1.30)

Example 3: Next Consecutive /29 Block Progression

Base block = 192.168.10.0/29

Block 1: 192.168.10.0 to 192.168.10.7.
Block 2: 192.168.10.8 to 192.168.10.15.
Block 3: 192.168.10.16 to 192.168.10.23.

Final Answer: Next Block: 192.168.10.8/29

How to Use This Calculator

Enter your assigned /29 IP address or network identifier.

Select whether you prefer the First Usable IP (.1 offset) or Last Usable IP (.6 offset) as your default gateway.

Copy the complete list of 6 usable host addresses into your router or firewall configuration.

Review the next consecutive /29 boundary to avoid IP overlap.

Reference Table

Offset	Address Role	Typical Assignment	Configurable on Device
+0	Network Address	Subnet boundary identifier	No (Reserved)
+1	First Usable Host	Default Gateway (Router interface)	Yes
+2	Usable Host #2	Primary Firewall / Mail Server	Yes
+3	Usable Host #3	Secondary Firewall / Web Server	Yes
+4	Usable Host #4	VPN Gateway / Remote Access	Yes
+5	Usable Host #5	DNS / Management Interface	Yes
+6	Usable Host #6	Spare Server / Alternative Gateway	Yes
+7	Broadcast Address	Subnet broadcast destination	No (Reserved)

Frequently Asked Questions

Why does an ISP /29 block only give me 5 usable device addresses if there are 6 usable hosts?

While a /29 has 6 mathematically usable IP addresses, one address must be assigned to the router/firewall gateway interface to route traffic to the internet, leaving 5 addresses for customer servers or devices.

What is the dotted decimal subnet mask for a /29 network?

The subnet mask for a /29 prefix is 255.255.255.248.

What numbers can a /29 network address end in?

Because /29 blocks contain 8 addresses, the final octet of a /29 network address must always be a multiple of 8: 0, 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120, 128, 136, 144, 152, 160, 168, 176, 184, 192, 200, 208, 216, 224, 232, 240, or 248.

What is the wildcard mask for a /29 subnet?

The wildcard mask is 0.0.0.7.

How does a /29 compare to a /30 subnet?

A /30 provides 4 total addresses and only 2 usable hosts (primarily used for point-to-point links), whereas a /29 provides 8 total addresses and 6 usable hosts.