| Size | Comment |
|---|---|
| /29 | starter pack |
| /28 | usually enough |
| /27 | default allocation |
| /26 | usually enough |
| /25 | still a lot of IPs! |
| /24 | are you an organization? |
The current guideline is to allocate a /27 or smaller by default, keeping space for up to a /26 if possible. Don't allocate more than a /25 worth of addresses and please think before you allocate: If you are going to have 2-3 servers and two VPN-spaces, a /28 is enough to suit your needs. Same will go for most home-networks. This is not public internet, but our IPv4-space is valuable too! If you need a /24 or larger, please ask in the IRC chan or on the mailing list.
For example, if there is no /27 free, you can split up a /26 into two /27. If you are looking for a /27 but there are none showing in the Open Netblocks tool, instead pick one of the /26 and click Take it! When registering your inetnum, instead of writing 172.2x.xxx.0-172.2x.xxx.63 then you can write 172.2x.xxx.0-172.2x.xxx.31. This will get you a /27 and save our IP space for others.
To register for example 172.20.150.0/27, you need to fill in 172.20.150.0-172.20.150.31.
{
"prefixes": {
"29": [
"172.20.183.32_29",
"172.21.76.96_29",
"172.22.127.144_29",
"172.22.129.192_29",
"172.22.139.160_29",
"172.22.139.168_29",
"172.22.184.96_29",
"172.22.185.64_29",
"172.23.226.48_29",
"172.23.231.144_29",
"172.23.239.64_29",
"172.23.67.160_29",
"172.23.73.144_29",
"172.23.82.96_29",
"172.23.90.128_29"
],
"28": [
"172.20.139.224_28",
"172.21.105.144_28",
"172.21.117.224_28",
"172.22.127.128_28",
"172.23.119.240_28",
"172.23.159.128_28",
"172.23.226.128_28",
"172.23.226.32_28",
"172.23.231.128_28",
"172.23.51.0_28",
"172.23.67.128_28",
"172.23.67.144_28",
"172.23.73.128_28",
"172.23.82.64_28",
"172.23.82.80_28"
],
"27": [
"172.20.139.192_27",
"172.20.228.128_27",
"172.20.33.64_27",
"172.21.112.128_27",
"172.21.118.64_27",
"172.21.118.96_27",
"172.21.76.64_27",
"172.21.95.192_27",
"172.22.107.128_27",
"172.22.139.128_27",
"172.22.184.64_27",
"172.23.117.64_27",
"172.23.117.96_27",
"172.23.155.128_27",
"172.23.196.128_27"
],
"26": [
"172.20.145.64_26",
"172.20.155.192_26",
"172.20.31.128_26",
"172.21.104.192_26",
"172.22.133.192_26",
"172.22.160.128_26",
"172.22.183.0_26",
"172.23.123.64_26",
"172.23.124.128_26",
"172.23.128.64_26",
"172.23.221.64_26",
"172.23.236.128_26",
"172.23.236.192_26",
"172.23.76.192_26",
"172.23.82.0_26"
],
"25": [
"172.20.145.128_25",
"172.20.190.128_25",
"172.20.191.0_25",
"172.20.22.128_25",
"172.21.111.128_25",
"172.22.110.128_25",
"172.22.154.128_25",
"172.22.177.128_25",
"172.23.116.128_25",
"172.23.123.128_25",
"172.23.155.0_25",
"172.23.160.128_25",
"172.23.217.128_25",
"172.23.84.128_25",
"172.23.98.128_25"
],
"24": [
"172.20.136.0_24",
"172.20.146.0_24",
"172.20.226.0_24",
"172.20.57.0_24",
"172.21.87.0_24",
"172.21.88.0_24",
"172.22.104.0_24",
"172.22.163.0_24",
"172.22.178.0_24",
"172.23.154.0_24",
"172.23.179.0_24",
"172.23.191.0_24",
"172.23.55.0_24",
"172.23.56.0_24",
"172.23.65.0_24"
],
"23": [
"172.20.156.0_23",
"172.21.124.0_23",
"172.22.190.0_23",
"172.23.112.0_23",
"172.23.138.0_23",
"172.23.152.0_23",
"172.23.164.0_23",
"172.23.188.0_23",
"172.23.194.0_23",
"172.23.206.0_23",
"172.23.46.0_23",
"172.23.80.0_23"
]
},
"mtime": "2026-09-12T17:05:47Z"
}