Public IP Inside the Network

[Rickey369]

Hi All,

I came across a network where the Public IP is used at the inside interface of the Internet router connecting the firewall. 

Why public ip is used at the segment connecting the router and the firewall instead of having a private ip.

Please Help me understand.

Regards,

Rickey

[LJ Gabrillo]

Ah! so basically <FIREWALL>--<ROUTER>--<ISP>
Answer to that is the router or the router configuration is provided by the ISP. Depending on your internet subscription, this can happen.

The public IP range allocated for your company/network is what is behind the quote-en-quote  LAN of your router. The 'WAN' of your router is their network in w/c you have no allocation to.

[omz]

When a company is assigned public IPv4 addresses they can use the public addresses as they like i.e. address internal LAN and WAN with public IPs. But since NAT was developed to solve the problem of running out of public IPv4 addresses. Addressing LAN with public IPs would be a waste. 

Unless there is a design requirement to use a public IP on the inside interface.