Using public IP block on internal network?

[KapsZ28]

I've never been big into networking as I usually leave that to the Network Engineers. I've spent most of my career supporting large enterprises and I noticed that none of them were using 10.x.x.x, 172.x.x.x, or 192.x.x.x for computers on the internal network. I never thought much of it as I had no clue about private IP addresses.

I happen to be looking through some old documentation from a previous employee that has IP addresses for computers that needed AV protection installed. I did a WHOIS on the IP and see that the company does in fact own those public IP blocks, 159.x.x.x. So why would a company use public IP blocks on their internal network? None of these IP addresses are accessible from the public.

 

[wizdum]

They probably bought them up in the initial ipv4 landrush, when they were unsure of the future.

 

[RocketTech]

They probably bought them up in the initial ipv4 landrush, when they were unsure of the future.

Yup. Large corporations were allowed to buy IP blocks for every planned network device in their inventory plus more for future expansion. Some large companies bought/were issued entire Class A or Class B blocks. When IP addressing was starting up, the thought of exhausting the pool was nearly unthinkable.

 

[jadams]

We do some work for GE. GE own the whole 3.x.x.x block I believe. All of their server's ip's that I've worked on start with 3. Pretty lame.

 

[swatbat]

Yup. Large corporations were allowed to buy IP blocks for every planned network device in their inventory plus more for future expansion. Some large companies bought/were issued entire Class A or Class B blocks. When IP addressing was starting up, the thought of exhausting the pool was nearly unthinkable.

Yep some did this.

I've seen people use public IP ranges they didn't own as internal ones. Surprised it didn't cause a problem.