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ovn-controller - Man Page

Open Virtual Network local controller


ovn-controller [options] [ovs-database]


ovn-controller is the local controller daemon for OVN, the Open Virtual Network. It connects up to the OVN Southbound database (see ovn-sb(5)) over the OVSDB protocol, and down to the Open vSwitch database (see ovs-vswitchd.conf.db(5)) over the OVSDB protocol and to ovs-vswitchd(8) via OpenFlow. Each hypervisor and software gateway in an OVN deployment runs its own independent copy of ovn-controller; thus, ovn-controller’s downward connections are machine-local and do not run over a physical network.

Acl Logging

ACL log messages are logged through ovn-controller’s logging mechanism. ACL log entries have the module acl_log at log level info. Configuring logging is described below in the Logging Options section.


Daemon Options


Causes a file (by default, program.pid) to be created indicating the PID of the running process. If the pidfile argument is not specified, or if it does not begin with /, then it is created in .

If --pidfile is not specified, no pidfile is created.


By default, when --pidfile is specified and the specified pidfile already exists and is locked by a running process, the daemon refuses to start. Specify --overwrite-pidfile to cause it to instead overwrite the pidfile.

When --pidfile is not specified, this option has no effect.


Runs this program as a background process. The process forks, and in the child it starts a new session, closes the standard file descriptors (which has the side effect of disabling logging to the console), and changes its current directory to the root (unless --no-chdir is specified). After the child completes its initialization, the parent exits.


Creates an additional process to monitor this program. If it dies due to a signal that indicates a programming error (SIGABRT, SIGALRM, SIGBUS, SIGFPE, SIGILL, SIGPIPE, SIGSEGV, SIGXCPU, or SIGXFSZ) then the monitor process starts a new copy of it. If the daemon dies or exits for another reason, the monitor process exits.

This option is normally used with --detach, but it also functions without it.


By default, when --detach is specified, the daemon changes its current working directory to the root directory after it detaches. Otherwise, invoking the daemon from a carelessly chosen directory would prevent the administrator from unmounting the file system that holds that directory.

Specifying --no-chdir suppresses this behavior, preventing the daemon from changing its current working directory. This may be useful for collecting core files, since it is common behavior to write core dumps into the current working directory and the root directory is not a good directory to use.

This option has no effect when --detach is not specified.


By default this daemon will try to self-confine itself to work with files under well-known directories determined at build time. It is better to stick with this default behavior and not to use this flag unless some other Access Control is used to confine daemon. Note that in contrast to other access control implementations that are typically enforced from kernel-space (e.g. DAC or MAC), self-confinement is imposed from the user-space daemon itself and hence should not be considered as a full confinement strategy, but instead should be viewed as an additional layer of security.


Causes this program to run as a different user specified in user:group, thus dropping most of the root privileges. Short forms user and :group are also allowed, with current user or group assumed, respectively. Only daemons started by the root user accepts this argument.

On Linux, daemons will be granted CAP_IPC_LOCK and CAP_NET_BIND_SERVICES before dropping root privileges. Daemons that interact with a datapath, such as ovs-vswitchd, will be granted three additional capabilities, namely CAP_NET_ADMIN, CAP_NET_BROADCAST and CAP_NET_RAW. The capability change will apply even if the new user is root.

On Windows, this option is not currently supported. For security reasons, specifying this option will cause the daemon process not to start.

Logging Options


Sets logging levels. Without any spec, sets the log level for every module and destination to dbg. Otherwise, spec is a list of words separated by spaces or commas or colons, up to one from each category below:

  • A valid module name, as displayed by the vlog/list command on ovs-appctl(8), limits the log level change to the specified module.
  • syslog, console, or file, to limit the log level change to only to the system log, to the console, or to a file, respectively. (If --detach is specified, the daemon closes its standard file descriptors, so logging to the console will have no effect.)

    On Windows platform, syslog is accepted as a word and is only useful along with the --syslog-target option (the word has no effect otherwise).

  • off, emer, err, warn, info, or dbg, to control the log level. Messages of the given severity or higher will be logged, and messages of lower severity will be filtered out. off filters out all messages. See ovs-appctl(8) for a definition of each log level.

Case is not significant within spec.

Regardless of the log levels set for file, logging to a file will not take place unless --log-file is also specified (see below).

For compatibility with older versions of OVS, any is accepted as a word but has no effect.


Sets the maximum logging verbosity level, equivalent to --verbose=dbg.


Sets the log pattern for destination to pattern. Refer to ovs-appctl(8) for a description of the valid syntax for pattern.


Sets the RFC5424 facility of the log message. facility can be one of kern, user, mail, daemon, auth, syslog, lpr, news, uucp, clock, ftp, ntp, audit, alert, clock2, local0, local1, local2, local3, local4, local5, local6 or local7. If this option is not specified, daemon is used as the default for the local system syslog and local0 is used while sending a message to the target provided via the --syslog-target option.


Enables logging to a file. If file is specified, then it is used as the exact name for the log file. The default log file name used if file is omitted is /var/log/ovn/program.log.


Send syslog messages to UDP port on host, in addition to the system syslog. The host must be a numerical IP address, not a hostname.


Specify method as how syslog messages should be sent to syslog daemon. The following forms are supported:

  • libc, to use the libc syslog() function. Downside of using this options is that libc adds fixed prefix to every message before it is actually sent to the syslog daemon over /dev/log UNIX domain socket.
  • unix:file, to use a UNIX domain socket directly. It is possible to specify arbitrary message format with this option. However, rsyslogd 8.9 and older versions use hard coded parser function anyway that limits UNIX domain socket use. If you want to use arbitrary message format with older rsyslogd versions, then use UDP socket to localhost IP address instead.
  • udp:ip:port, to use a UDP socket. With this method it is possible to use arbitrary message format also with older rsyslogd. When sending syslog messages over UDP socket extra precaution needs to be taken into account, for example, syslog daemon needs to be configured to listen on the specified UDP port, accidental iptables rules could be interfering with local syslog traffic and there are some security considerations that apply to UDP sockets, but do not apply to UNIX domain sockets.
  • null, to discard all messages logged to syslog.

The default is taken from the OVS_SYSLOG_METHOD environment variable; if it is unset, the default is libc.

PKI Options

PKI configuration is required in order to use SSL for the connections to the Northbound and Southbound databases.

-p privkey.pem

Specifies a PEM file containing the private key used as identity for outgoing SSL connections.

-c cert.pem

Specifies a PEM file containing a certificate that certifies the private key specified on -p or --private-key to be trustworthy. The certificate must be signed by the certificate authority (CA) that the peer in SSL connections will use to verify it.

-C cacert.pem

Specifies a PEM file containing the CA certificate for verifying certificates presented to this program by SSL peers. (This may be the same certificate that SSL peers use to verify the certificate specified on -c or --certificate, or it may be a different one, depending on the PKI design in use.)

-C none

Disables verification of certificates presented by SSL peers. This introduces a security risk, because it means that certificates cannot be verified to be those of known trusted hosts.


When cacert.pem exists, this option has the same effect as -C or --ca-cert. If it does not exist, then the executable will attempt to obtain the CA certificate from the SSL peer on its first SSL connection and save it to the named PEM file. If it is successful, it will immediately drop the connection and reconnect, and from then on all SSL connections must be authenticated by a certificate signed by the CA certificate thus obtained.

This option exposes the SSL connection to a man-in-the-middle attack obtaining the initial CA certificate, but it may be useful for bootstrapping.

This option is only useful if the SSL peer sends its CA certificate as part of the SSL certificate chain. The SSL protocol does not require the server to send the CA certificate.

This option is mutually exclusive with -C and --ca-cert.


Specifies a PEM file that contains one or more additional certificates to send to SSL peers. peer-cacert.pem should be the CA certificate used to sign the program’s own certificate, that is, the certificate specified on -c or --certificate. If the program’s certificate is self-signed, then --certificate and --peer-ca-cert should specify the same file.

This option is not useful in normal operation, because the SSL peer must already have the CA certificate for the peer to have any confidence in the program’s identity. However, this offers a way for a new installation to bootstrap the CA certificate on its first SSL connection.

Other Options


Prints a brief help message to the console.


Prints version information to the console.


ovn-controller retrieves most of its configuration information from the local Open vSwitch’s ovsdb-server instance. The default location is db.sock in the local Open vSwitch’s "run" directory. It may be overridden by specifying the ovs-database argument as an OVSDB active or passive connection method, as described in ovsdb(7).

ovn-controller assumes it gets configuration information from the following keys in the Open_vSwitch table of the local OVS instance:


The chassis name to use in the Chassis table. Changing the system-id while ovn-controller is running is not directly supported. Users have two options: either first gracefully stop ovn-controller or manually delete the stale Chassis and Chassis_Private records after changing the system-id. Note that the chassis name can also be provided via the system-id-override file in the local OVN "etc" directory or via the -n command-line option. The following precedence is used: first, the command-line option is read; if not present, the system-id-override file is read; if not present, then the name configured in the database is used.


The hostname to use in the Chassis table.


The integration bridge to which logical ports are attached. The default is br-int. If this bridge does not exist when ovn-controller starts, it will be created automatically with the default configuration suggested in ovn-architecture(7). When more than one controllers are running on the same host, external_ids:ovn-bridge-CHASSIS_NAME should be set for each of them, pointing to a unique bridge. This is required to avoid controllers stepping on each others’ feet.


This configuration is optional. If set, then the datapath type of the integration bridge will be set to the configured value. If this option is not set, then ovn-controller will not modify the existing datapath-type of the integration bridge.


The OVN database that this system should connect to for its configuration, in one of the same forms documented above for the ovs-database.


A boolean value that tells if ovn-controller should monitor all records of tables in ovs-database. If set to false, it will conditionally monitor the records that is needed in the current chassis.

It is more efficient to set it to true in use cases where the chassis would anyway need to monitor most of the records in OVN Southbound database, which would save the overhead of conditions processing, especially for server side. Typically, set it to true for environments that all workloads need to be reachable from each other.

NOTE: for efficiency and scalability in common scenarios ovn-controller unconditionally monitors all sub-ports (ports with parent_port set) regardless of the ovn-monitor-all value.

Default value is false.


The inactivity probe interval of the connection to the OVN database, in milliseconds. If the value is zero, it disables the connection keepalive feature.

If the value is nonzero, then it will be forced to a value of at least 1000 ms.


The encapsulation type that a chassis should use to connect to this node. Multiple encapsulation types may be specified with a comma-separated list. Each listed encapsulation type will be paired with ovn-encap-ip.

Supported tunnel types for connecting hypervisors and gateways are geneve, vxlan, and stt.

Due to the limited amount of metadata in vxlan, the capabilities and performance of connected gateways and hypervisors will be reduced versus other tunnel formats.


The IP address that a chassis should use to connect to this node using encapsulation types specified by external_ids:ovn-encap-type. Multiple encapsulation IPs may be specified with a comma-separated list.

In scenarios where multiple encapsulation IPs are present, distinct tunnels are established for each remote chassis. These tunnels are differentiated by setting unique options:local_ip and options:remote_ip values in the tunnel interface. When transmitting a packet to a remote chassis, the selection of local_ip is guided by the Interface:external_ids:encap-ip from the local OVSDB, corresponding to the VIF originating the packet, if specified. The Interface:external_ids:encap-ip setting of the VIF is also populated to the Port_Binding table in the OVN SB database via the encap column. Consequently, when a remote chassis needs to send a packet to a port-binding associated with this VIF, it utilizes the tunnel with the appropriate options:remote_ip that matches the ip in Port_Binding:encap. This mechanism is particularly beneficial for chassis with multiple physical interfaces designated for tunneling, where each interface is optimized for handling specific traffic associated with particular VIFs.


indicates the DF flag handling of the encapulation. Set to true to set the DF flag for new data paths or false to clear the DF flag.


A list of key-value pairs that map a physical network name to a local ovs bridge that provides connectivity to that network. An example value mapping two physical network names to two ovs bridges would be: physnet1:br-eth0,physnet2:br-eth1.


ovn-encap-csum indicates that encapsulation checksums can be transmitted and received with reasonable performance. It is a hint to senders transmitting data to this chassis that they should use checksums to protect OVN metadata. Set to true to enable or false to disable. Depending on the capabilities of the network interface card, enabling encapsulation checksum may incur performance loss. In such cases, encapsulation checksums can be disabled.


ovn-encap-tos indicates the value to be applied to OVN tunnel interface’s option:tos as specified in the Open_vSwitch database Interface table. Please refer to Open VSwitch Manual for details.


A list of options that will be consumed by the CMS Plugin and which specific to this particular chassis. An example would be: cms_option1,cms_option2:foo.


The transport zone(s) that this chassis belongs to. Transport zones is a way to group different chassis so that tunnels are only formed between members of the same group(s). Multiple transport zones may be specified with a comma-separated list. For example: tz1,tz2,tz3.

If not set, the Chassis will be considered part of a default transport zone.


A list of key-value pairs that map a chassis specific mac to a physical network name. An example value mapping two chassis macs to two physical network names would be: physnet1:aa:bb:cc:dd:ee:ff,physnet2:a1:b2:c3:d4:e5:f6. These are the macs that ovn-controller will replace a router port mac with, if packet is going from a distributed router port on vlan type logical switch.


The boolean flag indicates if the chassis is used as an interconnection gateway.


The boolean flag indicates if ovn-controller needs to check ovn-northd version. If this flag is set to true and the ovn-northd’s version (reported in the Southbound database) doesn’t match with the ovn-controller’s internal version, then it will stop processing the southbound and local Open vSwitch database changes. The default value is considered false if this option is not defined.


The time, in milliseconds, to wait before clearing flows in OVS after OpenFlow connection/reconnection during ovn-controller initialization. The purpose of this wait is to give time for ovn-controller to compute the new flows before clearing existing ones, to avoid data plane down time during ovn-controller restart/upgrade at large scale environments where recomputing the flows takes more than a few seconds or even longer. It is difficult for ovn-controller to determine when the new flows computing is completed, because of the dynamics in the cloud environments, which is why this configuration is provided for users to adjust based on the scale of the environment. By default, it is 0, which means clearing existing flows without waiting. Not setting the value, or setting it too small, may result in data plane down time during upgrade/restart, while setting it too big may result in unnecessary extra control plane latency of applying new changes of CMS during upgrade/restart. In most cases, a slightly bigger value is not harmful, because the extra control plane latency happens only once during the OpenFlow connection. To get a reasonable range of the value setting, it is recommended to run the below commands on a node in the target environment and then set this configuration to twice the value of Maximum shown in the output of the second command.

  • ovn-appctl -t ovn-controller inc-engine/recompute
  • ovn-appctl -t ovn-controller stopwatch/show flow-generation

The boolean flag indicates if ovn-controller should enable/disable the logical flow in-memory cache it uses when processing Southbound database logical flow changes. By default caching is enabled.


When used, this configuration value determines the maximum number of logical flow cache entries ovn-controller may create when the logical flow cache is enabled. By default the size of the cache is unlimited.


When used, this configuration value determines the maximum size of the logical flow cache (in KB) ovn-controller may create when the logical flow cache is enabled. By default the size of the cache is unlimited.


When used, this configuration value sets the minimum number of entries in the logical flow cache starting with which automatic memory trimming is performed. By default this is set to 10000 entries.


When used, this configuration value sets the percentage from the high watermark number of entries in the logical flow cache under which automatic memory trimming is performed. E.g., if the trim watermark percentage is set to 50%, automatic memory trimming happens only when the number of entries in the logical flow cache gets reduced to less than half of the last measured high watermark. By default this is set to 50.


When used, this configuration value specifies the time, in milliseconds, since the last logical flow cache operation after which ovn-controller performs memory trimming regardless of how many entries there are in the cache. By default this is set to 30000 (30 seconds).


The boolean flag indicates if ovn-controller when create tunnel ports should set local_ip parameter. Can be heplful to pin source outer IP for the tunnel when multiple interfaces are used on the host for overlay traffic. This is also useful when running multiple ovn-controller instances on the same chassis, in which case this setting will guarantee that their tunnel ports have unique configuration and can exist in parallel.


When used, this configuration value specifies the maximum timeout (in seconds) between two consecutive GARP packets sent by ovn-controller. ovn-controller by default sends just 4 GARP packets with an exponential backoff timeout. Setting external_ids:garp-max-timeout-sec allows to cap for the exponential backoff used by ovn-controller to send GARPs packets.

Most of configuration options listed above can also be set for a particular chassis name (see external_ids:system-id for more information). This can be achieved by setting external_ids:option-[chassis] instead of external_ids:option. For example, set external_ids:ovn-encap-ip-otherhv to use a particular IP address for the controller instance named otherhv. Name specific configuration options always override any global options set in the database.

Chassis-specific configuration options in the database plus the ability to configure the chassis name to use via the system-id-override file or command line allows to run multiple ovn-controller instances with unique chassis names on the same host using the same vswitchd instance. This may be useful when running a hybrid setup with more than one CMS managing ports on the host, or to use different datapath types on the same host. Make sure you also set external_ids:ovn-set-local-ip when using such configuration. Also note that this ability is highly experimental and has known limitations (for example, stateful ACLs are not supported). Use at your own risk.

ovn-controller reads the following values from the Open_vSwitch database of the local OVS instance:

datapath-type from Bridge table

This value is read from local OVS integration bridge row of Bridge table and populated in other_config:datapath-type of the Chassis table in the OVN_Southbound database.

iface-types from Open_vSwitch table

This value is populated in external_ids:iface-types of the Chassis table in the OVN_Southbound database.

private_key,  certificate,  ca_cert, and bootstrap_ca_cert from SSL table

These values provide the SSL configuration used for connecting to the OVN southbound database server when an SSL connection type is configured via external_ids:ovn-remote. Note that this SSL configuration can also be provided via command-line options, the configuration in the database takes precedence if both are present.

Open Vswitch Database Usage

ovn-controller uses a number of external_ids keys in the Open vSwitch database to keep track of ports and interfaces. For proper operation, users should not change or clear these keys:

external_ids:ovn-chassis-id in the Port table

The presence of this key identifies a tunnel port within the integration bridge as one created by ovn-controller to reach a remote chassis. Its value is the chassis ID of the remote chassis.

external_ids:ct-zone-* in the Bridge table

Logical ports and gateway routers are assigned a connection tracking zone by ovn-controller for stateful services. To keep state across restarts of ovn-controller, these keys are stored in the integration bridge’s Bridge table. The name contains a prefix of ct-zone- followed by the name of the logical port or gateway router’s zone key. The value for this key identifies the zone used for this port.

external_ids:ovn-localnet-port in the Port table

The presence of this key identifies a patch port as one created by ovn-controller to connect the integration bridge and another bridge to implement a localnet logical port. Its value is the name of the logical port with type set to localnet that the port implements. See external_ids:ovn-bridge-mappings, above, for more information.

Each localnet logical port is implemented as a pair of patch ports, one in the integration bridge, one in a different bridge, with the same external_ids:ovn-localnet-port value.

external_ids:ovn-l2gateway-port in the Port table

The presence of this key identifies a patch port as one created by ovn-controller to connect the integration bridge and another bridge to implement a l2gateway logical port. Its value is the name of the logical port with type set to l2gateway that the port implements. See external_ids:ovn-bridge-mappings, above, for more information.

Each l2gateway logical port is implemented as a pair of patch ports, one in the integration bridge, one in a different bridge, with the same external_ids:ovn-l2gateway-port value.

external-ids:ovn-l3gateway-port in the Port table

This key identifies a patch port as one created by ovn-controller to implement a l3gateway logical port. Its value is the name of the logical port with type set to l3gateway. This patch port is similar to the OVN logical patch port, except that l3gateway port can only be bound to a particular chassis.

external-ids:ovn-logical-patch-port in the Port table

This key identifies a patch port as one created by ovn-controller to implement an OVN logical patch port within the integration bridge. Its value is the name of the OVN logical patch port that it implements.

external-ids:ovn-startup-ts in the Bridge table

This key represents the timestamp (in milliseconds) at which ovn-controller process was started.

external-ids:ovn-nb-cfg in the Bridge table

This key represents the last known OVN_Southbound.SB_Global.nb_cfg value for which all flows have been successfully installed in OVS.

external-ids:ovn-nb-cfg-ts in the Bridge table

This key represents the timestamp (in milliseconds) of the last known OVN_Southbound.SB_Global.nb_cfg value for which all flows have been successfully installed in OVS.

external_ids:ovn-installed and external_ids:ovn-installed-ts in the Interface table

This key is set after all openflow operations corresponding to the OVS interface have been processed by ovs-vswitchd. At the same time a timestamp, in milliseconds since the epoch, is stored in external_ids:ovn-installed-ts.

Ovn Southbound Database Usage

ovn-controller reads from much of the OVN_Southbound database to guide its operation. ovn-controller also writes to the following tables:


Upon startup, ovn-controller creates a row in this table to represent its own chassis. Upon graceful termination, e.g. with ovs-appctl -t ovn-controller exit (but not SIGTERM), ovn-controller removes its row.


Upon startup, ovn-controller creates a row or rows in this table that represent the tunnel encapsulations by which its chassis can be reached, and points its Chassis row to them. Upon graceful termination, ovn-controller removes these rows.


At runtime, ovn-controller sets the chassis columns of ports that are resident on its chassis to point to its Chassis row, and, conversely, clears the chassis column of ports that point to its Chassis row but are no longer resident on its chassis. The chassis column has a weak reference type, so when ovn-controller gracefully exits and removes its Chassis row, the database server automatically clears any remaining references to that row.


At runtime, ovn-controller updates the MAC_Binding table as instructed by put_arp and put_nd logical actions. These changes persist beyond the lifetime of ovn-controller.

Runtime Management Commands

ovs-appctl can send commands to a running ovn-controller process. The currently supported commands are described below.


Causes ovn-controller to gracefully terminate.


Lists each local logical port and its connection tracking zone.


Lists each meter table entry and its local meter id.


Lists each group table entry and its local group id.

inject-pkt microflow

Injects microflow into the connected Open vSwitch instance. microflow must contain an ingress logical port (inport argument) that is present on the Open vSwitch instance.

The microflow argument describes the packet whose forwarding is to be simulated, in the syntax of an OVN logical expression, as described in ovn-sb(5), to express constraints. The parser understands prerequisites; for example, if the expression refers to ip4.src, there is no need to explicitly state ip4 or eth.type == 0x800.


Show OVN SBDB connection status for the chassis.


Trigger a full compute iteration in ovn-controller based on the contents of the Southbound database and local OVS database.

This command is intended to use only in the event of a bug in the incremental processing engine in ovn-controller to avoid inconsistent states. It should therefore be used with care as full recomputes are cpu intensive.


Reset southbound database cluster status when databases are destroyed and rebuilt.

If all databases in a clustered southbound database are removed from disk, then the stored index of all databases will be reset to zero. This will cause ovn-controller to be unable to read or write to the southbound database, because it will always detect the data as stale. In such a case, run this command so that ovn-controller will reset its local index so that it can interact with the southbound database again.

debug/delay-nb-cfg-report seconds

This command is used to delay ovn-controller updating the nb_cfg back to OVN_Southbound database. This is useful when ovn-nbctl --wait=hv is used to measure end-to-end latency in a large scale environment. See ovn-nbctl(8) for more details.


Flushes the ovn-controller logical flow cache.


Displays logical flow cache statistics: enabled/disabled, per cache type entry counts.


Display ovn-controller engine counters. For each engine node the following counters have been added:

  • recompute
  • compute
  • abort
inc-engine/show-stats engine_node_name counter_name

Display the ovn-controller engine counter(s) for the specified engine_node_name. counter_name is optional and can be one of recompute, compute or abort.


Reset ovn-controller engine counters.

Referenced By

ovn-architecture(7), ovn-nb(5), ovn-sb(5).

OVN 24.03.2 OVN Manual