/29 Subnet Mask ReferenceIPv4
Eight addresses wide, six of them usable: mask <code>255.255.255.248</code>. The /29 is the polite way to hand someone 'a few public IPs', enough for a router, a firewall pair, and a virtual IP or two.
/29 facts at a glance
- Subnet mask
- 255.255.255.248
- Wildcard mask
- 0.0.0.7
- Binary mask
- 11111111.11111111.11111111.11111000
- Total addresses
- 8
- Usable hosts
- 6 (excludes network & broadcast)
- Block size
- 8 addresses (23)
- Typical role
- Subnets, VLANs and WAN links
Example /29 networks
Three consecutive /29 blocks, starting at the /29 boundary that contains 198.51.100.0:
| Network | Usable range | Usable hosts |
|---|---|---|
| 198.51.100.0/29 | 198.51.100.1 – 198.51.100.6 | 6 |
| 198.51.100.8/29 | 198.51.100.9 – 198.51.100.14 | 6 |
| 198.51.100.16/29 | 198.51.100.17 – 198.51.100.22 | 6 |
How to calculate a /29 mask
A /29 mask sets the first 29 bits of a 32-bit number to 1 and leaves the remaining 3 bits as 0. In binary that reads 11111111.11111111.11111111.11111000, which converts to dotted decimal 255.255.255.248. Each block covers a contiguous run of 23 = 8 addresses, and every block starts at a multiple of that size. The wildcard simply flips every bit, giving 0.0.0.7.
Where /29 is used
- Small public blocks leased to businesses by their ISP.
- A DMZ with just a couple of externally reachable services.
- Outbound NAT pools with several source addresses.
In the .0 block, hosts occupy .1 through .6 while .0 names the network and .7 broadcasts.
Address efficiency is 75 percent: better than a /30's 50 percent, though still no match for RFC 3021's /31 on pure point-to-point duty.
Frequently asked questions
How many usable hosts are in a /29?
6 of 8 total addresses.
What is the subnet mask for a /29?
<code>255.255.255.248</code>, wildcard <code>0.0.0.7</code>: five fixed bits in the last octet leave three host bits.
How many /29s fit in a /24?
Thirty-two, since each consumes eight fourth-octet values.
If my ISP gives me x.x.x.0/29, what can I actually use?
Addresses .1 through .6 on your edge devices; .0 stays the network identifier and .7 remains the broadcast within that link segment.
Open this block in a calculator
Open the /29 block in the subnet calculator