Doc: OSPF graceful restart options

	tick <num>;

	ecmp <switch> [limit <num>];

	merge external <switch>;

	graceful restart <switch>|aware;

	graceful restart time <num>;

	area <id> {

		stub;

		nssa;

	from different LSAs are treated as separate even if they represents the

	same destination. Default value is no.

	<tag><label id="ospf-graceful-restart">graceful restart <m/switch/|aware</tag>

	When an OSPF instance is restarted, neighbors break adjacencies and

	recalculate their routing tables, which disrupts packet forwarding even

	when the forwarding plane of the restarting router remains intact.

	<rfc id="3623"> specifies a graceful restart mechanism to alleviate this

	issue. For OSPF graceful restart, restarting router originates

	Grace-LSAs, announcing intent to do graceful restart. Neighbors

	receiving these LSAs enter helper mode, in which they ignore breakdown

	of adjacencies, behave as if nothing is happening and keep old routes.

	When adjacencies are reestablished, the restarting router flushes

	Grace-LSAs and graceful restart is ended.

	This option controls the graceful restart mechanism. It has three

	states: Disabled, when no support is provided. Aware, when graceful

	restart helper mode is supported, but no local graceful restart is

	allowed (i.e. helper-only role). Enabled, when the full graceful restart

	support is provided (i.e. both restarting and helper role). Note that

	proper support for local graceful restart requires also configuration of

	other protocols. Default: aware.

	<tag><label id="ospf-graceful-restart-time">graceful restart time <m/num/</tag>

	The restart time is announced in the Grace-LSA and specifies how long

	neighbors should wait for proper end of the graceful restart before

	exiting helper mode prematurely. Default: 120 seconds.

	<tag><label id="ospf-area">area <M>id</M></tag>

	This defines an OSPF area with given area ID (an integer or an IPv4

	address, similarly to a router ID). The most important area is the