Posted on August 17, 2020 11:29 am
 |  Asked by Gréta Molnár
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I configured sflow, and it works for packet coming from ethernet interfaces, but i didn’t see any packets coming from vxlan tunnels.

Is this supported?

Answered on August 17, 2020 11:49 am

Hi Greta,

Thank you for contacting Arista.

Sflow works for only Physical ports. Vxlan interface is a logical interface so we cannot sample packets passing through vxlan interfaces.

However Vxlan Packets will be sampled when they are ingressing the switch on a physical interface and sampling wont happen after Vxlan decapsulation.



Posted by Gréta Molnár
Answered on August 17, 2020 12:19 pm

Is this true when recirculation used too?

The decapsulated vxlan packet ingress is an unconnectedethernet port, which "physical".

Its maybe a software limitation? I think recirculation channels and unconnected ethernet ports missing from snmp counters too.

Posted by Alexis Dacquay
Answered on August 18, 2020 11:07 am

Recirculation isn't used for VXLAN bridging, only the Trident2-based switch series 7050X required recirculation for VXLAN routing (but not for bridging). Other newer platforms don't need recirculation.
I didn't think of the recirculation sFlow sampling, I wouldn't be surprised if it doesn't work because:
- it is a bit special, traffic don't actually goes OUT or IN, the "ports" are rather for their internal pipeline resources, so traffic doesn't come IN like normal ports. That would be an explanation
I haven't tested but if you have tested on a recent software and it doesn't work then I would trust that.


Answered on September 2, 2020 12:17 pm

Hi Greta,

I have tested this in lab with latest EOS version on 7050 switches.I couldn't see the Vxlan Packets getting sampled after decapsulation in the packet captures on unconnected Ethernet ports.

As Alexis mentioned Recirc-Channel interfaces are a logical grouping of Ethernet and UnconnectedEthernet interfaces for use in recirculating the packet to provide features that require recirculation for Vxlan Routing and the ports are rather used for internal pipeline resources.

SNMP with Recirc-Channels is not supported.

You can refer to the below TOI for more information regarding Recirculation-channels and limitations:




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