Re: [libvirt] The config of IP address for 'macvtap' network

On 05/15/2012 05:33 AM, Michal Privoznik wrote: If only the guest will use the interface, that isn't necessary. As a matter of fact, once an interface has been assigned to a guest using macvtap passthrough mode, the host *can't* use the interface (it can continue to use it in the other macvtap modes, however), so it's completely pointless to configure an IP address for that interface on the host. A network device being used for a guest macvtap connection only needs an IP address set on the host if the host will also be using that interface - the guest does not magically acquire/use the IP address that has been set on the host, it needs its own IP address, configured on the guest in the same fashion you would configure any other guest interface (keep in mind that even in macvtap 'bridge' mode, the host and guest cannot communicate with each other via a macvtap interface). Otherwise, it's enough for the interface to be defined on the host (it may also be necessary for it to be "up" if it's a vlan device - I haven't tried macvtap with vlans). If you are using RHEL or Fedora, you can do any/all of that configuration with the virsh iface-define command. For example, here is the xml file that would define an "eth0.8" interface on a host (This is *not* the <interface> element of a domain configuration): <interface type="vlan" name="eth0.8"> <start mode="none"/> <protocol family="ipv4"> <ip address="192.168.43.1"/> </protocol> <vlan tag="8"> <interface name="eth0"/> </vlan> </interface> To get this defined in the system, you would use: virsh iface-define eth0.8.xml But again, it seems doubtful this is what you really want. No. The IP address used by the host for that interface (if any) should be configured in the normal manner of the host system. The IP address used by any guests using this interface / network based on this interface should be configured in the guest just as you would any other interface (if the guest is configured to get its IP address from DHCP, then you would need to have a DHCP server running *on a different host* connected to the .8 vlan. (BTW, note that in passthrough mode, only a single guest can connect to each physical device, so having a <network> defined for passthrough mode is mostly only useful if you have a pool of devices available. The way you have it defined above, only a single guest would be able to use that network.)