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

Thomas Narten <narten@us.ibm.com> Thu, 02 February 2012 15:11 UTC

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To: Lizhong Jin <lizho.jin@gmail.com>
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Comments: In-reply-to Lizhong Jin <lizho.jin@gmail.com> message dated "Thu, 02 Feb 2012 22:47:06 +0800."
Date: Thu, 02 Feb 2012 10:09:40 -0500
From: Thomas Narten <narten@us.ibm.com>
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Cc: yu.jinghai@zte.com.cn, dc@ietf.org
Subject: Re: [dc] Requirement for a method to manage mac address in DC
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Lizhong Jin <lizho.jin@gmail.com> writes:

> The VMs connected by SPB-M or NVO3/VXLAN/NVGRE will still reside in one L2
> network,

But those L2 networks are generally scoped to only include the VMs of one
tenant/customer. So a) the number of VMs is smallish (not the entire
data center), and b) any collisions will have been caused by the tenant
and only impact the tenant (not other tenants).

I'm not saying address collisions are  never a problem, but the above
reduces the frequency and limits the impact.

> and the VMs MAC will still conflict if have same MAC address. VM
> MAC confliction could not be mitigated or solved by these mechanism if I
> understand correctly.

Overlay approaches hide client/customer MACs inside a second, outer
header. Thus, if two different tenants use the same VM MAC address,
that collision is not visible within the datacenter, because the data
center network only uses the addresses in the outer header.

Thomas

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