How can I tell if an IP address is dynamic?
Although not a foolproof method, one way to determine if an IP address is dynamic is to look it up in the SORBS Dynamic User List and Host List (DUHL). The DUHL contains most netblocks of dynamically-assigned addresses by ISPs.
As an example, I'll determine if 18.104.22.168 is a dynamic IP by looking it up in the SORBS DUHL.
- dig method:
$ dig +short 22.214.171.124.dul.dnsbl.sorbs.net 127.0.0.10
- nslookup method:
nslookup 126.96.36.199.dul.dnsbl.sorbs.netNon-authoritative answer: Name: 188.8.131.52.dul.dnsbl.sorbs.net Address: 127.0.0.10
A result of 127.0.0.10 indicates it is in the SORBS DUHL list.