Is there any data on packet duplication?

Saku Ytti saku at
Tue Jun 23 07:03:00 UTC 2020

On Tue, 23 Jun 2020 at 09:54, William Herrin <bill at> wrote:

> There's a link in the chain you haven't explained. The packet which
> entered at S3 has a unicast destination MAC address. That's what was
> in the arp table. If they're following the standards, only one of PE1
> and PE2 will accept packets with that destination mac address. The
> other, recognizing that the packet is not addressed to it, drops it.

There are many reasons why practical devices (such as VXR) don't use
MAC HW filters. Such as your PHY runs out of HW filter slots, or the
HW does not support per-vlan HW filter, or there is 1 subinterface
with EoMPLS configured or other type of L2 service, requiring
reception of any DMAC.
There are also many reasons why both routers have the DMAC in their HW
filter, such as VRRP, HSRP.

> for example. But then this ring configuration doesn't exist in an AWS
> VPC and I've not particularly observed a lot of packet duplication out
> of Amazon.

Amazon does nothing standard, it's all AMZN.

Hope this helps!

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