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From Sergey Levitskiy <>
Subject Re: Auto Generating MAC Addresses for VMs in a given pattern
Date Thu, 11 May 2017 17:57:14 GMT
Randomization is done for each VM. The only static part is prefix - 06. Unless you change the
ACS code it won’t support a predefined range for Mac addresses. If you sort you nics table
by IP address you will see that octet on the rigtht gets incremented due to respective sequence
increment. But at the same time second and third octet on the left change due to randomization.

On 5/11/17, 10:44 AM, "Imran Ahmed" <> wrote:

    Hi Sergey,
    I am grateful for your prompt reply. The data center provider has provided a starting
sequence to be used. Do you think it would be another option to modify the sequence in db
tables (data_center and user_ip_address) so that the VMs get an IP/MAC from that sequence?
Is  the randomization function called during creation of each VM  or its run just once during
the creation of zone (data_center)?
    Kind regards,
    -----Original Message-----
    From: Sergey Levitskiy [] 
    Sent: Thursday, May 11, 2017 10:16 PM
    Subject: Re: Auto Generating MAC Addresses for VMs in a given pattern
    Mac address is dynamically created based on the IP address sequence number being allocated
on your subnet with randomization algorithm.
    It is done in 
        public static long createSequenceBasedMacAddress(final long macAddress) {
            return macAddress | 0x060000000000l | (long)s_rand.nextInt(32768) << 25
& 0x00fffe000000l;
    Starting sequence of your address is defined in data_center table and carried over to
user_ip_address tablewhere it gets properly incremented.
    Routers use slightly different pattern for mac addresses.
    I would advise to figure out another way of addressing your issue vs modifying ACS code
that deals with MACs.
    On 5/11/17, 9:27 AM, "Imran Ahmed" <> wrote:
        Dear Team,
        We are in a situation where the datacenter provider has put a restriction on
        the MAC addresses.
        We Cloudstack 4.3 with XenServers 6.5 .  We need to modify the pattern in
        which the guest VMs get the MAC address and use the pattern provided by the
        datacenter provider.
        Please suggest what should be a good starting point ?
        Best regards,

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