DHCP server issues in cloud data center environment

[Riku Meskanen]

Hello,

On 5 Mar 2014, at 11:10, Liang LR Rong <jet.rongl at cn.ibm.com> wrote:

> Do you hear of any other open-source DHCP server support such requirements?

I'm not sure you understand your seemingly simple question (a requirement you state) hides.

You need to understand first that dhcp service process binding IP-address and listening interface for the request doesn't work in isolation. They need an operating system support which handles ip address assignment on an interface, routing and all that fancy jazz underneath.

To get your requirement working it would first need the OS to have multiple separate routing tables (VRF's in Cisco terms, VirtualRouters/Routing Instances in Juniper world and Network namespaces in Linux) for each separate customer. Once you have that, then would be next hurdle to get the desired _one_ dhcpd process understand all that you had built. 

You need to understand that changes to dhcpd service would be major changes, a whole new abstraction layer routing instance and support it in running process, configuration and lease databases. 

Knowing that doesn't (at least not yet) exist I think you need to run one dhcpd per instance.

That isn't so bad you may initially think as even if you run many instances of same binary in a system such as Linux which supports shared memory w/ COW, you end up having n instances of same binary running sharing code segment(s) and each process having just its own data and stack segments, which means that you don't lose so much memory than you think first even when you run multiple instances of the same software in the same system.

:-) riku

ps.	this makes me thing my past suggestion to have a easy way of tagging separate dhcpd processes instances logged lines … without that it's going to be realy fun trying to find out which of those tens, hundreds or thousands of dhcpd instances logged what, especially when you have same private IP ranges reused over and over again, but that's another issue someone who gets that far will certainly find amusing :)

https://lists.isc.org/pipermail/dhcp-hackers/2012-October/001991.html

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