Re: [dc] Requirement for a method to manage mac address in DC

In a virtualized environment MAC addresses are not totally random generated. 
There is some notion of Management-Entity(s)/controller(s) allocating the 
MAC addresses for VMs and ensures that it does not assign the same MAC 
address to two different VMs and this work only within the scope of that 
management/controller administration. There are some exceptions of course 
(a) MAC address exhaustion under a given OUI category (b) manual 
copy/cloning of VMs and powering on them using standalone management 
entities (c) VMs that use MAC address override for legitimate reasons 
[because else things like licensing software breaks]. There are some 
mechanisms in place to address (a), but (b) and (c) requires co-operation at 
the management-entity/controllers. 

Mallik 

----- Original Message -----

From: "Truman Boyes" <tboyes@gmail.com> 
To: "Thomas Narten" <narten@us.ibm.com> 
Cc: "yu jinghai" <yu.jinghai@zte.com.cn>, dc@ietf.org, "Lizhong Jin" <lizho.jin@gmail.com> 
Sent: Thursday, February 2, 2012 10:20:07 AM 
Subject: Re: [dc] Requirement for a method to manage mac address in DC 

On Thu, Feb 2, 2012 at 10:55 AM, Thomas Narten < narten@us.ibm.com > wrote: 

Truman Boyes < tboyes@gmail.com > writes: 

> The L2 separation between multiple tenants is true in most circumstances in 
> DCs, but in commodity computing (ie. VPS, low cost dedicated servers, or 
> co-location) there is a concern on IPv4 address exhaustion or waste, so 
> machines/instances are grouped on single L2 segments. It is possible to 
> have virtual MAC overlaps on these segments. Is this something that this 
> group wishes to evaluate options to solve? 

IMO, this is putting the cart before the horse. 

Can we first get a sense for how big a problem this is in practice and 
whether existing mitigation approaches are not sufficient? 

I.e., is this a real problem causing significant pain today, or are 
their other bigger "pain points" that we should be looking at? 

Thomas 

In the VPS/VM world, I would say it's not a significant issue because there are single entities (Organizations) that manage the MAC addresses. Typically software would just increment the virtual MACs, and this does not require external protocols to ensure uniqueness. If there are many provisioning systems that manage VMs on the same network segment then they will need to keep their database in sync. 

-- 
--truman 

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