I'M GETTING CONFUSED ABOUT IPV4/IPV6, FLOATING IPS AND HOT-PLUGGING. CAN YOU PROVIDE A SIMPLE EXPLANATION FOR ALL THESE?
Sure, we 'll try to answer your questions in a Q&A style:
Q: Well, uhm, what is an IP in the first place?
A: An IP address is a unique numerical address that is assigned to a device
that participates to a computer network.
Q: There is more than one computer network?
A: The most known computer network is, of course, the Internet, but
there are other computer networks that you may encounter in your everyday life.
Take for instance the Wi-fi of your house, where your smartphone and laptop are
connected to your router. This forms a computer network between those two
devices.
Q: So, the Internet is considered as a public network whereas my house is
more of a private network?
A: Exactly. We use the same terminology in ~okeanos global too. A public IP of a
VM is an IP that can be reached from anywhere, whereas a private IP is an IP
that can be reached only by VMs that participate in the same private network.
Q: Ok, got that, but why do I see two IPs for my VM, IPv4 and IPv6?
A: It's not only your VM. All modern network cards have two IP addresses
and most probably your PC has two right now. We suggest you read this Mashable
article (yes also in Q&A
style, we were that picky) to help you understand the reason why there are
two.
Q: OK, got it. There are two addresses for any device and we will soon
transit to the IPv6 protocol due to the scarcity of IPv4 addresses. Does this
affect me as an ~okeanos global user?
A: Unfortunately yes. As you may have noticed in your usage stats, the number of the
available IPv4 addresses is less than the number of your VMs. Your VMs are not
left without an IP address of course, as they still retain their IPv6 address.
Q: Is it a problem if my VM has only an IPv6 address?
A: Well, given that the adoption rate of IPv6 is slow, there may be sites
that are not accessible via IPv6. Also, you may not be able to access your VM,
if your router isn't setup to handle IPv6 connections. This is not a common
issue nowadays, but for old configurations it may happen.
Q: Ouch, I don't like that. Is there anything we can do about it?
A: Yes, we have what we call floating IPs. Floating IPs are IPv4
addresses that can be assigned to any VM you want on-the-fly. This means that
when you want to connect to one of your VMs, you can detach a floating IP from
another VM and attach it to it. This happens in a matter of seconds using NIC
hot-plugging, so it shouldn't interrupt your workflow. You can take a look
at the floating IPs guide
to see how it's done. Also, remember that you can connect your machines to a
private network, which is faster and safer, if you want VM-to-VM communication.
Q: Private networks and floating IPs do not cover my use case. I need all
my VMs to be accessible from the Internet at the same time.
A: In this case, we would suggest you create a project where you formally
make a request for more resources (floating IPs in this case). Else, you will
need to resort to more expert solutions, such as using a VM of yours to route
traffic to the rest of your VMs (you can find more information on our NAT
guide).
Q: I see. One more question, what is NIC hot-plugging?
A: Let's explain first what hot-plugging is. hot-plugging is an OS feature
that allows you to register devices the moment they are connected to the
system. A common example is your USB drive, which you can plug and unplug
without rebooting your computer.
NIC (Network Interface Controller) hot-plugging is essentially the hot
plugging of a specific device, the network card. When a network card is plugged
in a running system that supports hot-plugging, it is registered immediately by
the OS and the Network Manager of your VM should assign an IP address to it.
Note: ~okeanos global images have been thoroughly tested to support hot-plugging.
If however your OS or application does not work properly with hot-plugging, you
are advised to shut down your VM first, before attaching/detaching any IP.
CYCLADES QUESTIONS
General
- Can I modify the technical specifications of an already created VM?
- How can I recover my data from a VM that has been destroyed? Is there any way to restore my VM back to its previous state?
- If I disconnect from my account, do my Virtual Machines stop working?
- Why does my VM's image show up as "Deleted" in its details?
- Why was my VM deleted?
Connectivity
- What is the username and password of my VM?
- Can I change the provided domain name of my VM?
- How can I connect to the Windows/Linux VM that I have created?
- How can I access all my VMs using one public IP?
- Why X2Go does not work when trying to connect to my VM?
- Why X2Go does not work on MacOS X?
- Is there a way of creating a local network using my Virtual Machines?
- Is it possible to create a local network between Virtual Machines that have been created by different users?
- In which case would I need to connect to my VM through the console?
- My Windows machine is "Running" but I cannot connect to it.
- My VM does not seem to have a network adapter, even though it is connected to a network.
- My VM does not have a floating IP, even though Cyclades report so.
- My VM does not work properly with IPv6.
- I'm getting confused about IPv4/IPv6, floating IPs and hot-plugging. Can you provide a simple explanation for all these?
- Can I shutdown/reboot my VM internally?
- Why is port X closed? Is it blocked by design?
- How can I add my public SSH key in an existing VM?