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How to: ByteBlower server and its DHCP behaviour on the Management port.
Posted by Vincent De Maertelaere, Last modified by Dries Decock on 03 April 2018 01:54 PM

The ByteBlower can be configured to use DHCP on its management interface. Your DHCP server could be configured to provide a fixed IP address to the ByteBlower server.  Some DHCP Servers use the DUID option to hand out an IP address when it is provided, otherwise it will use the hardware address field.

In this case, the ByteBlower DHCP client behaviour changed when moving from ByteBlower OS versions 2.x (ByteBlower server versions < 2.0) to ByteBlower OS versions 3.x (ByteBlower server versions >= 2.0 and ByteBlower server [compatibility] versions >= 1.10.22). This article will explain why and what the reader can do to fix this.

MAC address vs DUID?

First some history on DHCP, if you're not interested in the DHCP history, just skip this section.

The Dynamic Host Configuration Protocol (DHCP) was based on the BOOTP protocol. The latter did have a fixed header which contained the hardware address. When BOOTP was superseeded by DHCP, the header - and thus the hardware address field - were kept. The hardware address field was one of the identifiers used by the DHCP server to identify the DHCP host. On Ethernet networks commonly the MAC address of the clients NIC is used.

When DHCPv6 was born, a new client identifier was also introduced: the Device Unique IDentifier (DUID). The DUID can be built using multiple mechanisms (e.g. hardware address, hardware address + time, ...). This allows the client to aquire multiple DHCPv6 addresses per interface! This is so flexible that the Client Identifier option was also included in a DHCP extention and DHCP server implementations prefer this Client IDentifier instead of the old hardware address field.

Some DHCP Servers use the BOOTP hardware address field unless they find a DUID option in the DHCP options.  Also a DHCP server cannot dissect a DUID to retrieve the hardware address.  This means that a ByteBlower server can switch IP addresses between 2 software versions!  To prevent this, they ByteBlower server can be configured how to form the DUID option.

ByteBlower Configuration

Most of the DHCP client software packages can be configured which type of identifier to include, what kind of DUID must be used. The DHCP client implementation ByteBlower OS uses, has the choice between clientid and duid. The Client ID is MAC based, the DUID is hardware address + time based.

This is a configuration option which changed when releasing ByteBlower 2.1.0 (running on ByteBlower OS 3.1.0), but can easily be modified on the ByteBlower server.

So if your DHCP server has troubles parsing the DUID, consider changing the ByteBlower DHCP configuration.

  1. Login using the console or SSH.
  2. Edit the dhcpcd.conf file with nano
    # nano /etc/dhcpcd.conf
  3. Find the line 
    #clientid
    and put it active:
    clientid
  4. Find the line:
    duid
    and put into comments:
    #duid
  5. Save and close the file using:
    Ctrl-o, Ctrl-x
  6. Reboot the ByteBlower Server
    # reboot

 

 

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