[PVE-User] NAT issues

Alexandre Kouznetsov alk at ondore.com
Fri Oct 19 00:49:16 CEST 2012

El 18/10/12 17:01, Samir Faci (Dev) escribió:
> Built in Proxmox support.  I didn't setup a DHCP server.
I did not knew there is a built-in DHCP server in Proxmox NAT networking 
model. Did you got this from any documentation?

According to http://pve.proxmox.com/wiki/Network_Model, NAT is a working 
setup, but need to be done manually, nothing built-in out-of-the-box. 
So, if you have not set up a DHCP server yourself and your VM still gets 
an IP, I would think it is set statically in the VM.

If so, no surprise you are getting the same IP after cloning the disk 
image, it's hardcoded.

> If I was using a DHCP server then I would be using Bridged mode.  That
> seems to work fine.  I have an issue with the NAT support.
> my understand was that proxmox would allocate IP and handle the
> NATing.

describes that in a quite clear way. For NAT mode, you still use the 
good old bridge configuration, except that the bridge will not contain 
any physical network interface. So, you VM will talk to your Proxmox 
host vi the bridge, Proxmox host will talk outside acting as gateway. 
It's up to you to set up the packet forwarding and NAT with iptables (or 
just routing). The documentation does not describe it, but it seems you 
could also put a DHCP server directly on the Proxmox host.

I have done such setups using Xen, very useful. By a personal choice, I 
do not set up a NAT gateway functionality directly on the host system, 
instead I deploy a dedicated VM as NAT router, DHCP/DNS server, etc.

> One more update.
> I created a new VM.. new disk, only constant is that I'm using the
> same Ubuntu ISO,
> created a NAT network device... I went through the installation
> process....and once again NAT gives me the same IP address.
Well, my imagination fails me here. I have no idea who provides the DHCP 
service in your setup. There is not supposed to be any, unless you have 
set it up yourself.

Could you please post the contents of /etc/network/interfaces file of 
your Proxmox node, "ifconfig -a" output and "brctl show" output?
I think there is something seriously twisted up there.

Alexandre Kouznetsov

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