CentOS virt - Aug 2010 - IP based VirtualHost: IP aliases vs. additional virtual interfaces

Hi,

I have a virtualized infrastructure based on KVM/QEMU with CentOS 5.5
x86_64 hosts and guests, using bridge networking.
I want to set up IP based VirtualHosts in Apache (because they will
use SSL) and I have ordered an IP block.

Now, in order to have the IPs available on some guests, I'm wondering
whether I should:
1 - add additional virtual interfaces
or
2 - set up IP aliases (eth0:1, etc.) in the guests

I imagine that (1) would be faster and more efficient (but that's a
guts feeling), and it feels cleaner.
But with (2), I just need to restart the network in order to add new
IPs (there won't be that many: like around 10 in the next few months),
insteead of restarting the whole guest.

Are there any best practices for adding IP-addresses to virtualized guests?

Thanks in advance for your insights!

Mathieu

On 08/10/2010 02:01 AM, Mathieu Baudier wrote:
> n order to have the IPs available on some guests, I'm wondering
> whether I should:
> 1 - add additional virtual interfaces
> or
> 2 - set up IP aliases (eth0:1, etc.) in the guests
>
> I imagine that (1) would be faster and more efficient (but that's a
> guts feeling), and it feels cleaner.
> But with (2), I just need to restart the network in order to add new
> IPs (there won't be that many: like around 10 in the next few months),
> insteead of restarting the whole guest.
>    
You don't have to restart the guest to add or remove aliases:

ifup eth0:1

ifdown eth0:1

work fine for starting and stopping them.

-- 
Benjamin Franz