What follows is a summary of the ways in which you can setup QEMU networking
1. Userspace SLIRP stack
Provides a virtual LAN with NAT to the outside world. The virtual network
has DHCP & DNS services and will give the guest VM addresses starting
from 10.0.2.15. The default router will be 10.0.2.2 and the DNS server
will be 10.0.2.3. This networking is the only option for unprivileged
users who need their VMS to have outgoing access. Example configs are:
<interface type='user'/>
<interface type='user'>
<mac address="11:22:33:44:55:66:/>
</interface>
2. Virtual network
Provides a virtual network using a bridge device in the host. Depending
on the virtual network configuration, the network may be totally isolated,
NAT'ing to aan explicit network device, or NAT'ing to the default route.
DHCP and DNS are provided on the virtual network in all cases and the
IP range can be determined by examining the virtual network config with
'virsh net-dumpxml <network name>'. There is one virtual network called
'default' setup out of the box which does NAT'ing to the default route
and has an IP range of 192.168.22.0/255.255.255.0. Each guest will
have an associated tun device created with a name of vnetN, which can
also be overriden with the <target> element. Example configs are
<interface type='network'>
<source network='default'/>
</interface>
<interface type='network'>
<source network='default'/>
<target dev='vnet7'/>
<mac address="11:22:33:44:55:66:/>
</interface>
3. Bridge to to LAN
Provides a bridge from the VM directly onto the LAN. This assumes there
is a bridge device on the host which has one or more of the hosts
physical NICs enslaved. The guest VM will have an associated tun device
created with a name of vnetN, which can also be overriden with the
<target> element. The tun device will be enslaved to the bridge. The
IP range / network configuration is whatever is used on the LAN. This
provides the guest VM full incoming & outgoing net access just like
a physical machine. Examples include
<interface type='bridge'>
<source dev='br0'/>
</interface>
<interface type='bridge'>
<source dev='br0'/>
<target dev='vnet7'/>
<mac address="11:22:33:44:55:66:/>
</interface>
4. Generic connection to LAN
Provides a means for the administrator to execute an arbitrary script
to connect the guest's network to the LAN. The guest will have a tun
device created with a name of vnetN, which can also be overriden with the
<target> element. After creating the tun device a shell script will be
run which is expected to do whatever host network integration is
required. By default this script is called /etc/qemu-ifup but can be
overriden.
<interface type='ethernet'/>
<interface type='ethernet'>
<target dev='vnet7'/>
<script path='/etc/qemu-ifup-mynet'/>
</interface>
5. Multicast tunnel
A multicast group is setup to represent a virtual network. Any VMs whose
network devices are in the same multicast group can talk to each other
even across hosts. This mode is also available to unprivileged users.
There is no default DNS or DHCP support and no outgoing network access.
To provide outgoing network access, one of the VMs should have a 2nd
NIC which is connected to one of the first 4 network types and do the
appropriate routing. The multicast protocol is compatible with that
used by user mode linux guests too. The source address used must be
from the multicast address block
<interface type='mcast'>
<source address='230.0.0.1' port='5558'/>
</interface>
6. TCP tunnel
A TCP client/server architecture provides a virtual network. One VM
provides the server end of the netowrk, all other VMS are configured
as clients. All network traffic is routed between the VMs via the
server. This mode is also available to unprivileged users.
There is no default DNS or DHCP support and no outgoing network access.
To provide outgoing network access, one of the VMs should have a 2nd
NIC which is connected to one of the first 4 network types and do the
appropriate routing.
Example server config
<interface type='server'>
<source address='192.168.0.1' port='5558'/>
</interface>
Example client config
<interface type='client'>
<source address='192.168.0.1' port='5558'/>
</interface>
NB, options 2 -> 4 are also supported by Xen VMs, so it is possible to
use these configs to have networking with both Xen & QEMU/KVMs connected
to each other.
Regards,
Dan.
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