Re: [Xen-devel] Best way to get IP addresses from VMs without logging in to them?

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-06-11 at 12:32 -0400, Russ Pavlicek wrote:
> I have been working on an "on-ramp" application to introduce new
> people to Xen Project (more on that later), when I ran into a simple
> scenario which seems to lack a simple solution:
> 
> When I start up a new VM which employs DHCP, how can I
> programmatically determine what IP address it obtained?
> 
> When I look at the Wiki, I find the following reference:
> 
> http://wiki.xenproject.org/wiki/Xen_FAQ_Networking#IP_Determination
> 
> Which suggests using tcpdump for sniffing out packets relating to a
> known MAC address.  But that depends on traffic flow from VM, which
> could be time consuming if the machine happens to be idle.

If the machine is using DHCP then you should be able to observe the DHCP
requests and responses, which contain the IP address. I think Xenrt does
something around parsing the tcpdump output of that happening, but I'm
not sure of the details.

Ian.



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