Hello, I am seeing more strange behavior on my test cluster. In this scenario I have created two L2 networks; two VMs on one compute node in the first L2 network; a third VM on another compute node in the second L2 network. Compute1 ============ L2 Net 1: ---------- VMa VMb Compute3 ============ L2 Net 2: ---------- VMc Pinging from VMa to VMc works as expected, but I can not ping from VMb to VMc at the same time. VMa -> VMc OK VMb -> VMc Broken If the ping from VMb is started first it works, but then the ping from VMa is broken. As can be seen in the packet dump, traffic from VMb reaches VMc but the return traffic is forwarded to VMa, which is incorrect. The destination MAC address of the return traffic is correct, but OpenvSwitch forwardeds the traffic to the wrong VM. You can see in the dump-flows on compute1, there is no flow to output 9, only a flow to output 5. I tested with agent_mode=dvr_no_external and with agent_mode=dvr with identical results. If I deploy a centralized router it works. In my opinion this is the same bug. Best Regards Phil tcpdump on VMs ========================================== DUMP VMa ------------------ eth0: link/ether fa:16:3e:e7:c3:cb inet 10.10.10.185/24 debian@debian:~$ sudo tcpdump -netti eth0 icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes 1592330132.615290 fa:16:3e:5b:19:10 > fa:16:3e:f9:c2:b7, ethertype IPv4 (0x0800), length 98: 10.10.20.57 > 10.10.10.242: ICMP echo reply, id 577, seq 33, length 64 1592330133.639309 fa:16:3e:5b:19:10 > fa:16:3e:f9:c2:b7, ethertype IPv4 (0x0800), length 98: 10.10.20.57 > 10.10.10.242: ICMP echo reply, id 577, seq 34, length 64 DUMP VMb ------------------ eth0: link/ether fa:16:3e:f9:c2:b7 inet 10.10.10.242/24 debian@debian:~$ sudo tcpdump -netti eth0 icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes 1592330136.797903 fa:16:3e:f9:c2:b7 > fa:16:3e:5b:19:10, ethertype IPv4 (0x0800), length 98: 10.10.10.242 > 10.10.20.57: ICMP echo request, id 577, seq 37, length 64 1592330137.821900 fa:16:3e:f9:c2:b7 > fa:16:3e:5b:19:10, ethertype IPv4 (0x0800), length 98: 10.10.10.242 > 10.10.20.57: ICMP echo request, id 577, seq 38, length 64 DUMP VMc ------------------ eth0: link/ether fa:16:3e:b2:47:43 inet 10.10.20.57/24 debian@debian:~$ sudo tcpdump -netti eth0 icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes 1592330137.026450 fa:16:3e:b2:47:43 > fa:16:3e:c0:43:39, ethertype IPv4 (0x0800), length 98: 10.10.20.57 > 10.10.10.242: ICMP echo reply, id 577, seq 38, length 64 1592330138.050433 fa:16:3e:c0:43:39 > fa:16:3e:b2:47:43, ethertype IPv4 (0x0800), length 98: 10.10.10.242 > 10.10.20.57: ICMP echo request, id 577, seq 39, length 64 1592330138.050461 fa:16:3e:b2:47:43 > fa:16:3e:c0:43:39, ethertype IPv4 (0x0800), length 98: 10.10.20.57 > 10.10.10.242: ICMP echo reply, id 577, seq 39, length 64 1592330139.074473 fa:16:3e:c0:43:39 > fa:16:3e:b2:47:43, ethertype IPv4 (0x0800), length 98: 10.10.10.242 > 10.10.20.57: ICMP echo request, id 577, seq 40, length 64 Flow dumps on comute node 1 ========================================== [root@compute1 ~]# ovs-appctl dpctl/show system@ovs-system: lookups: hit:3335 missed:233 lost:0 flows: 5 masks: hit:13026 total:4 hit/pkt:3.65 port 0: ovs-system (internal) port 1: br-ex (internal) port 2: enp3s0 port 3: br-int (internal) port 4: br-tun (internal) port 5: tapf494600d-62 port 6: vxlan_sys_4789 (vxlan: packet_type=ptap) port 7: qr-56f77029-3e (internal) port 8: qr-dfc3396a-66 (internal) port 9: tapbd3a7589-3f [root@compute1 ~]# ovs-appctl dpctl/dump-flows recirc_id(0),in_port(9),eth(src=fa:16:3e:f9:c2:b7,dst=fa:16:3e:5b:19:10),eth_type(0x0800),ipv4(frag=no), packets:493, bytes:48314, used:0.456s, actions:7 recirc_id(0),in_port(8),skb_mark(0x4000000),eth(src=fa:16:3e:c0:43:39),eth_type(0x0800),ipv4(tos=0/0x3,frag=no), packets:539, bytes:51618, used:0.456s, flags:P., actions:set(tunnel(tun_id=0x2,src=10.0.2.100,dst=10.0.2.102,ttl=64,tp_dst=4789,flags(df|key))),set(eth(src=fa:16:3f:9c:aa:5e)),set(skb_mark(0)),6 recirc_id(0),tunnel(tun_id=0x1,src=10.0.2.102,dst=10.0.2.100,flags(-df-csum+key)),in_port(6),eth(src=fa:16:3f:58:95:6f),eth_type(0x0800),ipv4(frag=no), packets:536, bytes:55028, used:0.455s, flags:P., actions:set(eth(src=fa:16:3e:5b:19:10)),5 recirc_id(0),in_port(2),eth(src=00:17:e0:1f:63:94,dst=00:17:e0:1f:63:94),eth_type(0x9000), packets:107, bytes:6420, used:0.318s, actions:drop Flow dumps on comute node 3 ========================================== [root@compute3 ~]# ovs-appctl dpctl/show system@ovs-system: lookups: hit:2090 missed:186 lost:0 flows: 7 masks: hit:6106 total:5 hit/pkt:2.68 port 0: ovs-system (internal) port 1: br-ex (internal) port 2: enp3s0 port 3: br-int (internal) port 4: br-tun (internal) port 5: qr-56f77029-3e (internal) port 6: qr-dfc3396a-66 (internal) port 7: vxlan_sys_4789 (vxlan: packet_type=ptap) port 8: tap447c86ea-d9 [root@compute3 ~]# ovs-appctl dpctl/dump-flows recirc_id(0),in_port(5),skb_mark(0x4000000),eth(src=fa:16:3e:5b:19:10),eth_type(0x0800),ipv4(tos=0/0x3,frag=no), packets:561, bytes:57478, used:0.299s, flags:P., actions:set(tunnel(tun_id=0x1,src=10.0.2.102,dst=10.0.2.100,ttl=64,tp_dst=4789,flags(df|key))),set(eth(src=fa:16:3f:58:95:6f)),set(skb_mark(0)),7 recirc_id(0),tunnel(tun_id=0x2,src=10.0.2.100,dst=10.0.2.102,flags(-df-csum+key)),in_port(7),eth(src=fa:16:3f:9c:aa:5e),eth_type(0x0800),ipv4(frag=no), packets:564, bytes:54068, used:0.299s, flags:P., actions:set(eth(src=fa:16:3e:c0:43:39)),8 recirc_id(0),in_port(2),eth(src=00:17:e0:1f:63:93,dst=01:00:0c:cc:cc:cc),eth_type(0/0xffff), packets:0, bytes:0, used:never, actions:drop recirc_id(0),in_port(2),eth(src=00:17:e0:1f:63:93,dst=00:17:e0:1f:63:93),eth_type(0x9000), packets:110, bytes:6600, used:5.755s, actions:drop recirc_id(0),in_port(6),eth(src=fa:16:3e:c0:43:39,dst=fa:16:3e:b2:47:43),eth_type(0x0806), packets:0, bytes:0, used:never, actions:8 recirc_id(0),in_port(2),eth(src=fa:16:3e:14:30:b5,dst=33:33:00:00:00:02),eth_type(0x8100),vlan(vid=97),encap(eth_type(0x86dd),ipv6(frag=no)), packets:0, bytes:0, used:never, actions:1 recirc_id(0),in_port(8),eth(src=fa:16:3e:b2:47:43,dst=fa:16:3e:c0:43:39),eth_type(0x0800),ipv4(frag=no), packets:561, bytes:57478, used:0.299s, flags:P., actions:6 recirc_id(0),in_port(8),eth(src=fa:16:3e:b2:47:43,dst=fa:16:3e:c0:43:39),eth_type(0x0806),arp(sip=10.10.20.57), packets:0, bytes:0, used:never, actions:6