On Tue, 23 Jun 2020 at 09:54, William Herrin <bill@herrin.us> 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! -- ++ytti