[ovs-discuss] Why OVS behaves difference between ovs-vswitchd and ovs-vswitchd-dpdk?

[Harry Lee]

Hello,

My server is running debian testing. I install two ovs version through apt:

```
openvswitch-switch/testing,unstable,now 2.15.0+ds1-2 amd64 [installed]
  Open vSwitch switch implementations

openvswitch-switch-dpdk/testing,unstable,now 2.15.0+ds1-2 amd64 [installed]
  DPDK enabled Open vSwitch switch implementation
```

Then I found something  difference between them.

Here's my experience:

```
# switch ovs version to ovs-vswitchd
update-alternatives --set ovs-vswitchd /usr/lib/openvswitch-common/ovs-vswitchd
/etc/init.d/openvswitch-switch restart
ip addr add 10.90.67.148/25 dev br0
ping 10.90.67.129  # network is ok

# switch ovs version to ovs-vswitchd-dpdk
update-alternatives --set ovs-vswitchd /usr/lib/openvswitch-switch-dpdk/ovs-vswitchd-dpdk
/etc/init.d/openvswitch-switch restart
ip addr add 10.90.67.148/25 dev br0
ping 10.90.67.129  # unreachable
```

The same configuration, using ovs-vswitchd was reachable while using ovs-vswitchd-dpdk was unreachable.

Then I used `tcpdump br0` to checkout if there are packets from br0, and I found some ARP packets:

```
root at debian:~# tcpdump -i br0 -nnn
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on br0, link-type EN10MB (Ethernet), snapshot length 262144 bytes
02:14:27.010265 ARP, Request who-has 10.90.67.129 tell 10.90.67.148, length 28
02:14:28.034127 ARP, Request who-has 10.90.67.129 tell 10.90.67.148, length 28
02:14:29.058128 ARP, Request who-has 10.90.67.129 tell 10.90.67.148, length 28
```

But when I ran `ovs-ofctl dump-flows br0`, I saw n_packets is 0:

```
root at debian:~# ovs-ofctl dump-flows br0
 cookie=0x0, duration=1016.243s, table=0, n_packets=0, n_bytes=0, priority=0 actions=NORMAL
```

Why does ovs-vswitchd-dpdk ignore the packet from br0? Does it need additional configuration?
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