[CentOS-virt] How to connect a guest to a fixed routable address?

Wed May 26 20:37:12 UTC 2010
James B. Byrne <byrnejb at harte-lyne.ca>

I am experimenting with kvm on a quad x86_64 running CentOS-5.5.  I
have created my first virtual guest and it seems to run fine.  Now I
wish to assign that particular guest to a fixed, public IP address. 
There seems to be at least two ways to proceed and I am soliciting
comments on the preferred approach.

In the first instance I can use brctl to create a bridged 'shared
physical device' and presumably add that device to the network
configuration of the guest, assigning the IP connection details

In the second, I can continue to use the virtual networking system,
albeit with fixed private as opposed to DHCP assigned addresses.  In
this case I gather that I must use ifconfig to add public IP
addresses to the eth0 interface of the host and use iptables to
route the public to the private address.

Firstly, are my inferences correct? Are there any other approaches
that I cannot discern? If these are the only two methods then which
is the preferred one?  I get the sense that bridging works in a
manner that permits only one guest to access that physical device,
however the documentation is not explicit on the matter.

I have looked extensively for guidance but I suspect that a great
deal of what I have read is somewhat dated and likely to cause me
more trouble than help.

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