| 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": [
"172.20.231.112_29",
"172.20.237.96_29",
"172.20.39.96_29",
"172.20.62.176_29",
"172.21.112.48_29",
"172.21.75.48_29",
"172.22.110.64_29",
"172.22.110.72_29",
"172.22.127.96_29",
"172.22.157.224_29",
"172.22.162.32_29",
"172.23.151.128_29",
"172.23.151.136_29",
"172.23.159.32_29",
"172.23.32.112_29"
],
"28": [
"172.20.15.240_28",
"172.20.159.128_28",
"172.20.170.128_28",
"172.20.184.160_28",
"172.20.184.208_28",
"172.20.2.192_28",
"172.20.229.96_28",
"172.20.231.96_28",
"172.20.62.160_28",
"172.21.106.128_28",
"172.21.123.128_28",
"172.21.75.32_28",
"172.22.129.32_28",
"172.22.167.32_28",
"172.23.32.96_28"
],
"27": [
"172.20.174.32_27",
"172.20.184.0_27",
"172.20.184.32_27",
"172.20.184.64_27",
"172.21.77.64_27",
"172.21.82.64_27",
"172.22.130.32_27",
"172.22.162.0_27",
"172.22.167.0_27",
"172.23.100.160_27",
"172.23.110.32_27",
"172.23.110.64_27",
"172.23.162.0_27",
"172.23.162.32_27",
"172.23.247.32_27"
],
"26": [
"172.21.106.0_26",
"172.21.91.0_26",
"172.22.106.0_26",
"172.22.177.0_26",
"172.22.183.0_26",
"172.23.100.192_26",
"172.23.104.0_26",
"172.23.158.128_26",
"172.23.173.192_26",
"172.23.193.192_26",
"172.23.221.192_26",
"172.23.221.64_26",
"172.23.230.128_26",
"172.23.41.0_26",
"172.23.93.128_26"
],
"25": [
"172.20.183.128_25",
"172.20.22.128_25",
"172.21.109.128_25",
"172.21.93.128_25",
"172.22.107.128_25",
"172.22.161.128_25",
"172.23.101.0_25",
"172.23.107.128_25",
"172.23.118.128_25",
"172.23.120.128_25",
"172.23.150.128_25",
"172.23.151.0_25",
"172.23.161.128_25",
"172.23.189.128_25",
"172.23.226.128_25"
],
"24": [
"172.20.23.0_24",
"172.22.104.0_24",
"172.22.116.0_24",
"172.22.126.0_24",
"172.22.166.0_24",
"172.22.173.0_24",
"172.22.176.0_24",
"172.23.115.0_24",
"172.23.121.0_24",
"172.23.154.0_24",
"172.23.155.0_24",
"172.23.166.0_24",
"172.23.176.0_24",
"172.23.216.0_24",
"172.23.243.0_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",
"172.23.122.0_23",
"172.23.138.0_23",
"172.23.152.0_23",
"172.23.164.0_23",
"172.23.174.0_23",
"172.23.194.0_23",
"172.23.206.0_23",
"172.23.210.0_23",
"172.23.46.0_23",
"172.23.80.0_23"
]
},
"mtime": "2025-11-18T16:04:11Z"
}