Problem: When a VM comes up with interface on localnet, external switches on the broadcast segment have to update their port->mac mappings and routers have to update their arp caches. This normally happens when the VM initiates traffic. on the localnet interface. But in some scenarios, when the VM remains silent, the VM is unreachable externally. This can happen when the VM is migrated or when the VM is reusing an earlier used IP but with a different mac. The fix is to for OVN to initiate gratuitous ARP which updates external routers/switches on localnet.
This problem has been reported at: https://bugs.launchpad.net/networking-ovn/+bug/1545897 What to generate: When ipv4 and mac are defined on the port, we can generate a gratuitous ARP request or a reply. ARP requests seem to be preferred over ARP replies as suggested here: https://tools.ietf.org/html/rfc5227#section-3 In this change, a broadcast garp reply is generated. How many to generate: 3 to 5 arps spaced over 1-2 minutes seems to be reasonable to allow for losses. For comparison qemu generates 5 rarps when a VM port comes up. In this change, the garp packet is input to the port, and goes through the pipelines. An alternative is to output directly onto the localnet patch port. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev