[P4-dev] P4 issues on mininet with multiple switches

Amedeo Sapio amedeo.sapio at polito.it
Sat May 6 16:29:07 EDT 2017

since you talk about acks, I assume you meant TCP and not UDP.
I had a similar experience using network namespaces (similar to what
mininet does). The destination host was receiving all the packets but it
did not send any ACK. The problem was that TCP offloading was active on the
virtual interfaces, so TCP packets had the wrong checksum. You can disable
it in each virtual interface used by mininet with the following 2 commands:

ethtool --offload ethX rx off tx off
ethtool -K ethX gso off

​using the name of your interface instead of ethX.

Hope this helps,

Amedeo Sapio

e-mail: amedeo.sapio at polito.it
Mobile: +39 3291564391

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> We have been trying to test the P4 implementation of ecmp for quite a
> while and have failed due to mininet causing problems with topologies
> containing multiple switches. For example, in our case, Host 1 is sending
> UDP packets and is Host 2 is receiving packets but not sending ACKS and
> hence , we cannot evaluate the performance of the protocol. Can you please
> guide us how to approach this problem?
> Regards,
> Hassan Ali Khan
> 2018-10-0116
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