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My research group has a multi-compute node HPC running ubuntu server 14.04.5 hosted at a home address (ISP is Comcast Xfinity). Internally, we use only one of the compute nodes. The machine can ping both IPv4 & IPv6 networks, so it seems the ISP is running dual stack and if I'm correct, both an IPv4 and IPv6 address should be assigned. The IPv6 address is available, and that is what we've been using, but the public IPv4 address is not being correctly activated or assigned. We've been using miredo (a Teredo tunneling service), but that requires that we (1) are on the IPv6 net or (2) use a Teredo tunnel remotely (e.g. use miredo on a remote Linux machine or use a tunnel broker service). Ideally, we would like to configure the machine/network such that the IPv4 address is also assigned and can be used (from say, a remote Windows machine on the IPv4 net - when IPv6 net is unavailable).

With ifconfig, the following is the line for em3 (not eth0 for some reason?):

inet addr:10.0.1.27  Bcast:10.0.1.255  Mask:255.255.255.0

This looks like the router assigned (local) address. If I run the following command, I do receive a public facing IPv4 address - so it seems that the ISP is serving one:

$ curl -4 icanhazip.com

Here are the contents of the /etc/network/interfaces file:

# The loopback network interface

auto lo

iface lo inet loopback



# The primary network interface

auto em3

iface em3 inet dhcp



# This is an autoconfigured IPv6 interface

iface em3 inet6 auto

My best guess from searching through help forums is that either the home router is not correctly serving the IP address or the machine itself is not properly receiving/configuring the address. The individual running the server has not been able to resolve this issue. Any thoughts? I'm happy to provide more information as needed - I know the information that I've provided is pretty limited. Any tools or commands that might help me diagnose the issue?

Thanks

Related questions:

How to set Ubuntu Server to ipv4 network address Here is a virtual server example of a similar situation. Static assignment of the IPv4 address doesn't seem like the correct solution.

IPv4 is not getting configured on Ubuntu in a dualstack (IPv4/IPv6) network Maybe this is relevant? Is there an equivalent to Require IPv4 addressing for this connection to complete on Ubuntu Server?

how to obtain ipv4 address of ubuntu server running in virtual box along with ipv6? Another virtual box. Solution has a bunch of commands, but I'm not sure. Disabling IPv6 doesn't seem like a good solution either.

My best guess from searching through help forums is that either the home router is not correctly serving the IP address or the machine itself is not properly receiving/configuring the address.

The IP's you posted (10.0.1.27) is RFC1918 address, commonly known as private IPs. They are commonly used for NAT.

You have a router that performs NATing in front of your computer, which explains the behavior. To get a public IP at the Linux machine, you have to turn of the NAT function of your router. Please refer to the manual of the router for instructions on this.

Alternatively, you may use port forwarding to forward traffic to the machine in question.