[CentOS-virt] Virtual NICs on a Xen VM

Thu Jun 28 14:22:46 UTC 2012
Steve Campbell <campbell at cnpapers.com>

Currently, I've got a Centos 5.8 host that I began playing with Xen 
virtual machines. It's a sandbox sort of server where I try and learn 
all of this virtualization stuff. In the future, I'll more than likely 
swith to Centos 6 and kvm, but for now, it's xen.

Searching google and the list, I can't find an explanation of how to add 
a second virtual NIC to a running VM when I only have one real NIC on 
the server. For the most part, in my searches it appears that I need a 
real second NIC on the server to do this. I can find a few examples, but 
each sort of implies it a one-to-one minimum of real hardware to virtual 

So what I'm asking  is "Is it possible to create a xen VM that has two 
virtual ethernet interfaces on a host that has only one real NIC"? I'd 
like to simulate a server that I can make a firewall out of and to do 
that would mean I need an internal and external interface. I'm 
attempting to create a set of firewalls in a highly available 
environment to test with. So far, most of the docs I find are for more 
complex people than I. There's concepts like virtual switches and the 
like that are creeping into the reading, so the more I read, the more 
overwhelmed I am.

Did I mention I'm still just starting to explore virtualization? If 
someone can provide me with a possible yes-no answer and maybe a link to 
documentation that might explain the way, I'll gladly do all my own 
grunt work.

Thanks for any and all help.

steve campbell