| 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": [
"172.20.133.160_29",
"172.20.133.168_29",
"172.20.15.48_29",
"172.20.184.160_29",
"172.20.23.64_29",
"172.21.122.64_29",
"172.21.122.72_29",
"172.21.122.96_29",
"172.22.181.144_29",
"172.23.125.8_29",
"172.23.168.0_29",
"172.23.168.8_29",
"172.23.177.48_29",
"172.23.40.104_29",
"172.23.40.96_29"
],
"28": [
"172.20.131.64_28",
"172.20.133.176_28",
"172.20.233.64_28",
"172.20.50.128_28",
"172.20.50.144_28",
"172.21.105.144_28",
"172.21.122.80_28",
"172.21.91.0_28",
"172.22.134.192_28",
"172.22.181.128_28",
"172.23.151.192_28",
"172.23.182.32_28",
"172.23.182.48_28",
"172.23.221.224_28",
"172.23.41.0_28"
],
"27": [
"172.20.133.192_27",
"172.20.187.128_27",
"172.20.187.160_27",
"172.20.23.32_27",
"172.20.237.96_27",
"172.21.65.128_27",
"172.21.68.128_27",
"172.21.68.160_27",
"172.22.106.0_27",
"172.22.106.32_27",
"172.22.148.128_27",
"172.22.148.160_27",
"172.22.154.96_27",
"172.23.221.192_27",
"172.23.48.32_27"
],
"26": [
"172.20.129.192_26",
"172.20.131.0_26",
"172.20.15.64_26",
"172.20.18.128_26",
"172.20.41.128_26",
"172.21.90.64_26",
"172.21.94.0_26",
"172.22.129.192_26",
"172.22.139.128_26",
"172.22.139.192_26",
"172.22.140.0_26",
"172.22.183.0_26",
"172.22.188.192_26",
"172.23.105.192_26",
"172.23.199.0_26"
],
"25": [
"172.20.164.128_25",
"172.20.187.0_25",
"172.21.93.128_25",
"172.22.106.128_25",
"172.22.154.128_25",
"172.23.107.128_25",
"172.23.150.128_25",
"172.23.151.0_25",
"172.23.167.128_25",
"172.23.228.128_25",
"172.23.58.128_25",
"172.23.67.128_25",
"172.23.73.128_25",
"172.23.76.128_25",
"172.23.90.128_25"
],
"24": [
"172.20.130.0_24",
"172.20.180.0_24",
"172.22.151.0_24",
"172.22.173.0_24",
"172.22.176.0_24",
"172.23.106.0_24",
"172.23.191.0_24",
"172.23.204.0_24",
"172.23.229.0_24",
"172.23.55.0_24",
"172.23.56.0_24",
"172.23.59.0_24",
"172.23.68.0_24",
"172.23.74.0_24",
"172.23.82.0_24"
],
"23": [
"172.20.60.0_23",
"172.21.124.0_23",
"172.22.174.0_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",
"172.23.206.0_23",
"172.23.210.0_23",
"172.23.46.0_23",
"172.23.80.0_23"
]
},
"mtime": "2025-12-25T22:10:15Z"
}