Re: [Qemu-discuss] qemu dhcp issue

[Donald R Laster Jr]

Vlad,

  Could you possibly need to set the MAC address of the Ethernet interfaces for the VM 
itself?  You are referencing "vendor ID" and I making an assumption that you 
are referencing the first 3 octets of the Ethernet MAC Address.  In case you are not 
aware of what a MAC address is defined as:

        MAC, Media Access Control, address is a globally unique identifier
        assigned to network devices, and therefore it is often referred to as
        hardware or physical address. MAC addresses are 6-byte (48-bits) in
        length, and are written in MM:MM:MM:SS:SS:SS format. The first 3-bytes
        are ID number of the manufacturer, which is assigned by an Internet
        standards body. The second 3-bytes are serial number assigned by the
        manufacturer. (http://www.iplocation.net/tools/mac-address.php)

  Redhat/CentOS when booted expect specific MAC addresses when certain things 
are configured.  QEMU may not be using the expected MAC addresses with the 
current changes - it will set a default.  The files to look are in 
subdirectories of the /etc/ directory.  NetworkManager might be the tool you 
need to look at as well.

  Check if you are configuring the VM's networking with similar settings:

   -net nic,macaddr=52:54:00:10:01:2E,vlan=0,model=e1000
   -net tap,vlan=0,helper=/usr/libexec/qemu-bridge-helper
    -net nic,macaddr=52:54:00:10:01:23,vlan=0,model=e1000
   -net tap,vlan=0,helper=/usr/libexec/qemu-bridge-helper

The key is to set the macaddr= field with the appropriate vendor ID.

   Don

Vlad Yasevich wrote on 01/20/2015 06:10 PM:
> On 01/20/2015 08:51 AM, czebartek wrote:
> > Hi All,
> > I have a problem with configuration of dhcp client on VM started by qemu. I 
> > have a server connected to some LAN network from where I get IP addresses. On 
> > my server I start qemu with prepared kernel image and rootfs. I set up tap 
> > interfaces and bridge on a host machine. The machine I'am simulating is Linux 
> > Centos 6.
> > What is the problem now:
> > When qemu starts up it starts some dhcp client and request the IP address from 
> > our external dhcp server. But, there were some security changes in dhcp server 
> > recently and now accepts requests only from clients with specific vendor ID.
> > The thing is that I don't know how qemu is starting the dhcp client and which client it 
> > is using. On Centos there is "dhclient". I know that it uses dhclient.conf file 
> > when I could set up vendor ID, but even if I set this config it doesn't work.
> > Do you know how to check whcih dhcp client is started when qemu starts VM ? Do 
> > you know how to check what configuration it is using ?
> > Thanks in advance for help.
> > Best regards,
> >   Bartosz
>
> In this case, qemu doesn't start the dhcp client on the vm.  The OS instance
> running within the VM will start the dhcp client and it's whatever is installed 
> for that
> instance. So, look to see what is installed inside the VM and edit appropriate 
> files.
>
> -vlad

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