[CentOS-virt] IP aliases from a QEMU/KVM guest

Dennis J. dennisml at conversis.de
Fri Aug 13 15:33:35 EDT 2010


On 08/13/2010 04:48 PM, Mathieu Baudier wrote:
>> NETMASK=255.255.255.255?
>
> it surprised me as well first, but that is what OVH recommends and it
> works fine with virtual interfaces

That just means that the connected "network" contains only one machine.
Depending on the actual topology this might be a bit inefficient but 
probably not in a serious way.

Sending traffic from 192.168.0.10 to 192.168.0.11 with a netmask of 
255.255.255.0 will result in the traffic flowing directly between the 
machines because the system knows the target is part of the same subnet.

Using 255.255.255.255 as netmask means the system will no longer see the 
target as part of the same subnet and as a result will send the traffic to 
the default gateway instead which will then forward it to the target.

Regards,
   Dennis


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