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I believe I've setup the Ubuntu MAAS cluster controller correctly and it's configured to use managed DHCP & DNS (maas-dhcp & maas-dns). Seems to work reasonably well but I'm seeing the following possible bugs/issues:

  1. It seems like the DHCP server has skipped a particular IP address in the middle of the range, for some reason it doesn't like the .23 IP address within the Class C. Reviewing the /var/lib/maas/dhcp/dhcpd.leases file it's never issued this IP address. Given that this is on a private/backbone Ethernet switch it's not that anything else has used this address.
  2. It seems like the DHCP server has begun the dynamic IP issuance starting from .21 even though the MAAS "Edit Cluster Interface" screen clearly indicates .20 as the "DHCP dynamic IP range low value". Reviewing the leases file shows that it's never been issued.
  3. When PXE-booting the third/fourth/fifth nodes I'm seeing that the DHCP server has a fondness of re-issuing the same IP addresses .24 and .25, for example. Reviewing the leases I see that occasionally there's an "ends..." line which presumably is issuing a short-lived (30-second) IP address to a newly-seen node; this is to be expected. But there are sometimes when it's issued a 12-hour IP address lease to a node that's been named; this feels like it's a possible issue that's re-using the same IP addresses.

Of course, it's possible that I don't yet understand the nuances of the MAAS DHCP strategy of issuing IP addresses to a pool of resources.

I include here one of the paragraphs from dhcpd.leases for review:

lease 10.100.100.24 {
  starts 4 2015/09/03 18:19:03;
  ends 5 2015/09/04 06:19:03;
  cltt 4 2015/09/03 18:19:03;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 00:1d:09:9a:5f:4f;
  client-hostname "psi";
}

Perhaps naively I started writing down the node name versus the issued IP address in a worksheet for tracking. And I considered labeling the nodes with their issued IP addresses. Or are IP addresses in this setup just too dynamic for this style of management?

Ubuntu 14.0.4.2LTS64bit
maas:
  Installed: 1.7.6+bzr3376-0ubuntu2~14.04.1
maas-dns:
  Installed: 1.7.6+bzr3376-0ubuntu2~14.04.1
maas-dhcp:
  Installed: 1.7.6+bzr3376-0ubuntu2~14.04.1
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  • "Presumably, this is the expected behavior." (I added this a few days ago but the comment was deleted.) Sep 23, 2015 at 20:40

1 Answer 1

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As you may know, DHCP is really all about re-use of IP addresses, so you shouldn't be surprised by this behaviour. Providing no address is handed out when there's already an active lease, and addresses are being handed out when requested, DHCP is doing its job. The DHCP specifications don't set out rules as to the order of assignment of addresses, so although one might expect them to be handed out in a monotonically increasing sequence, there's no constraint on a server to do this.

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  • I've been at this project for about four weeks now and I'm beginning to finally see how DHCP works within the MAAS/OpenStack arrangement. It's not necessarily well-documented though within the MAAS pages. Sep 19, 2015 at 23:39

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