Refer to the exhibit.
Which statement correctly explains the bgp graceful-restart command?
A.
This command is used to enable NSR and is entered on the NSR-capable router, and also on
any NSR-aware peer
B.
This command is used to enable NSF and is entered on the NSF-capable router, and also on
any NSF-aware peer
C.
This command is only required on the NSF-capable routers to enable BGP graceful restart with
the BGP peers
D.
This command is only required on the NSF-aware routers to enable BGP graceful restart with
the BGP peers
E.
This command is only required on the NSR-capable routers to enable BGP graceful restart with
the BGP peers
When Graceful Restart is used, peer networking devices are informed, via protocol extensions prior to the event, of the SSO capable routers ability to perform graceful restart. The peer device must have the ability to understand this messaging. When a switchover occurs, the peer will continue to forward to the switching over router as instructed by the GR process for each particular protocol, even though in most cases the peering relationship needs to be rebuilt. Essentially, the peer router will give the switching over router a “grace” period to re-establish the neighbor relationship, while continuing to forward to the routes from that peer.
http://www.cisco.com/c/en/us/products/collateral/ios-nx-os-software/high-availability/solution_overview_c22-487228.html
BGP support for Cisco NSF requires that neighbor routers are NSF-aware or NSF-capable. Cisco NSF awareness in BGP is also enabled by the graceful restart mechanism. A router that is NSF-aware functions like a router that is NSF-capable, with one exception: an NSF-aware router is incapable of performing an SSO operation. However, a router that is NSF-aware is capable of maintaining a peering relationship with a NSF-capable neighbor during an NSF SSO operation, as well as holding routes for this neighbor during the SSO operation.