Description of L3 agent configuration options

Configuration option = Default value	Description
[DEFAULT]
agent_mode = legacy	(StrOpt) The working mode for the agent. Allowed modes are: 'legacy' - this preserves the existing behavior where the L3 agent is deployed on a centralized networking node to provide L3 services like DNAT, and SNAT. Use this mode if you do not want to adopt DVR. 'dvr' - this mode enables DVR functionality and must be used for an L3 agent that runs on a compute host. 'dvr_snat' - this enables centralized SNAT support in conjunction with DVR. This mode must be used for an L3 agent running on a centralized node (or in single-host deployments, e.g. devstack)
allow_automatic_l3agent_failover = False	(BoolOpt) Automatically reschedule routers from offline L3 agents to online L3 agents.
enable_metadata_proxy = True	(BoolOpt) Allow running metadata proxy.
external_network_bridge = br-ex	(StrOpt) Name of bridge used for external network traffic.
gateway_external_network_id =	(StrOpt) UUID of external network for routers implemented by the agents.
handle_internal_only_routers = True	(BoolOpt) Agent should implement routers with no gateway
router_id =	(StrOpt) If namespaces is disabled, the l3 agent can only configure a router that has the matching router ID.
send_arp_for_ha = 3	(IntOpt) Send this many gratuitous ARPs for HA setup, if less than or equal to 0, the feature is disabled