Would I have any issues if I use a private network range in between an edge network with public ip's?

ie: (internet)<---> ip)<---><---> edge with public ips)

I suspect no based on my understanding, but I want to crazy check myself.


  • Is there NAT between public and privte IP ?
    – DavidM
    Jan 12 '16 at 10:52
  • Yes. And a vpn to an AWS server to monitor the private networks devices. We are currently using public ips all the way to the edge and I think we could save a significant amount of public IP's by implementing a private address scheme in the middle.
    – Helkas
    Jan 12 '16 at 15:43

It can be done and generally works ok. It's quite common to see it in cable TV networks. There are a couple of caveats though.

  1. If the machines on the intermediate networks need access to the internet then NAT will be needed. The NAT implementation must be flexible enough to decide based on source IP whether or not to NAT (linux NAT certainly is, I don't know about other implementations).
  2. ICMP replies sent by the routers will be generated with private source addresses and may end up getting blocked. This may cause issues with things like traceroute and path MTU discovery. As long as you don't have any low-mtu segments this shouldn't be a massive issue though.

You can use private IP between two public IP network as long as you do not send to the internet packets with a private address as source.

It's quite common.


It'll work fine, and you're best off not eating up precious public IPv4 addresses for this kind of thing anyway (I assume since you are using a /30 that it is purely an interconnect network between two layer 3 network devices.

One way to think about it is that it's just a means for the two devices on either end of your segment to have a common LAN segment to exchange traffic across (one being the next hop of the other's routes, and vice versa). So long as they can communicate together (and aren't actually hosting any resources themselves), it doesn't matter to the outside world what IPs they use.

You'll just have to keep in mind that the relevant interfaces won't be directly monitorable from the internet, which can be a plus or a minus depending on what exactly you are trying to do.

  • Thanks Jeremy. Tried to upvote but it only let me upvote the first 2. All good answers.
    – Helkas
    Jan 12 '16 at 15:45

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