[ 2.0rc1] MAAS should tell the user if a external DHCP server is detected, specially when deploying a machine with 'Auto-Assign'

[Dave Chiluk]

I have a flat network with a router/gateway/dns/dhcp server at 192.168.1.1. I have disabled dhcp in maas, under networks -> untagged vlan -> disable dhcp.

My Nodes are all set to auto assign.

It is my opinion that when dhcp is disabled for the vlan that a node is on, and the node is set to auto-assign, maas should rely on the upstream dns/dhcp for IP address. Otherwise maas is acting like a dhcp server even though it may not be running dhcpd. This is bad default behavior.

In my case, maas was auto-assigning IPs to my maas nodes that were already dhcp assigned to other non-maas nodes in my network.

This is similar to https://bugs.launchpad.net/maas/+bug/1519090

[Dave Chiluk (chiluk)]

The not-so-obvious workaround for this issue is to change the IP Address assignment method to DHCP for every node.

[Blake Rouse (blake-rouse)]

Any reason you marked this a security bug?

This is the expected behavior. MAAS is a IPAM system, so if the subnet is defined we assigned IP address. If you want that behavior you set the interface to DHCP and it will DHCP. That is not the default configuration and is not recommended. It is recommended to use "Auto assign" which does static IP address assignment.

If you want to use static IP address assignment with an external DHCP server, you just need to reserve the other devices that have static IP address in that subnet, and define the dynamic ranges that the external DHCP server is using.

[Andres Rodriguez (andreserl)]

Agreed with Blake here.

If you se the interface to:
 * Auto-assign means that MAAS will provide IP addresses and e/n/i will be written for the specific interface with the auto-asigned IP address.
 * DHCP means that you can use a external DHCP server.

That being said, the solution to your issue is to change the interfaces to DHCP in order for you to use the external DHCP server.

[Dave Chiluk (chiluk)]

I understand where you guys are coming from. I understand that using external dhcp and dns servers have lead to maas node's IPs to change and as a result taking down clouds.

In my use case, I was able to install maas, disable maas's dhcp, enlist nodes, and start deploying my nodes. MAAS happily stomped all over the IPs of machines I already had deployed.

Yes it can be configured away by setting DHCP on each of the nodes. Could it be smarter definitely.

One suggestion might be to have four options under the dhcp configuration, enable dhcp, disable dhcp, use external dhcp server for all assignment, and external dhcp with maas static assigned partitioned network.

Another suggestion, and the one I like most is that when you disable the DHCP server, force the user to configure static IP reserved ranges maas, and inform maas of the dhcp server's address space. Maybe also have a check-box here for never assign static addresses.

[Andres Rodriguez (andreserl)]

Maybe to make this even simpler, we should simply put a notification that "No DHCP server is configured in MAAS, if you have your own DHCP ensure XYZ happens"

[Dave Chiluk (chiluk)]

I'll leave the particulars up to your team, but I think you understand the kind of trouble I got myself in.

I was thinking more along the lines of the current deployment ui-flow, where you click deploy, and then are given options on what OS to deploy. Something similar to that would be nice where you click disable dhcp server, and you are given the entry boxes that need to be thought about *and maybe a notification explaining why they are being show).

[Adam Collard (adam-collard)]

This bug has not seen any activity in the last 6 months, so it is being automatically closed.

If you are still experiencing this issue, please feel free to re-open.

MAAS Team