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I could eventually get all ips my isp is using by restarting my router and writing down the ips I get but that's very time consuming, so is there any way to get ip pool of my isp?

Dragonknigh
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1 Answers1

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No, you couldn't. That's because the DHCP server of your ISP leases the IP address for you for a period of time and during that lease time you'll get the same IP. Because that also applies to all other customers, some may held the same IP for months, preventing you to ever get it. Your method is both impractical and based on false assumptions.

The only certain way to get every IP address of your ISP (or every IP address they have reserved to the customer pool your connection is using) is to ask them. Allowing that pool on some firewall could be a reasonable reason to ask for that information, and it's shouldn't be a huge secret.

Another way is to utilize the whois database to get all IP addresses in the same IP block. If your address was 198.51.100.77, lookup for the IP gives you information on the range an its owner:

NetRange:       198.51.100.0 - 198.51.100.255
CIDR:           198.51.100.0/24
NetName:        TEST-NET-1
NetHandle:      NET-198-51-100-0-1
Parent:         NET198 (NET-198-0-0-0-0)
NetType:        IANA Special Use
OriginAS:
Organization:   Internet Assigned Numbers Authority (IANA)

The limitation of that method is that your ISP may have other independent ranges. So, ask them.

Esa Jokinen
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  • Thanks. I've read somewhere that isp's buy/rent eg. 5k IPs and use them for all its users, so one IP could be used by multiply users. I guess thats wrong... – Dragonknigh Oct 10 '17 at 15:48
  • A user may have a public IP or be behind a NAT, depending on the connection and its purpose. For connection designed for business networks (or home servers) it's possible to get a static IP, while most DSL connections have a dynamic public IP. Then, mobile connections might be behind a NAT in order to save IPv4 addresses. – Esa Jokinen Oct 10 '17 at 15:53
  • Do big residential buildings use NAT, so 1000s of people use same public IP? – Dragonknigh Oct 11 '17 at 11:55