Which statements accurately describe OSPF Graceful Restart (when the restarting router is able to Keep its forwarding tables across the restart)? (Select two.)

Statement (A) is correct because the OSPF Graceful Restart (GR) helper role is a less resource-intensive function supported on all ArubaOS-CX platforms, including the 6100 series. This allows lower-end switches to participate in and support network stability during a neighbor's restart. Statement (B) is correct as it describes a fundamental requirement for high availability in a VSF stack. For a VSF stack to perform a "hitless" or "graceful" failover (nonstop routing) using OSPF GR when the commander fails, a secondary (standby) member must be present to take over the control plane operations seamlessly while the data plane continues forwarding traffic.

C. BFD and OSPF GR are not mutually exclusive. They can be configured together, but a BFD session failure will immediately tear down the OSPF adjacency, overriding the GR grace period.
D. This statement is imprecise. The restarting router sends Grace-LSAs, while only GR-aware neighbors (helpers) listen for and process them. Routers not supporting GR will ignore them.
E. The requirement for a secondary member applies when the VSF stack is the restarting entity to ensure nonstop routing. A VSF stack acting as a GR helper for another router does not have this requirement.

1. ArubaOS-CX 10.12 VSF Guide, Page 10, Section: "VSF high availability".

Quote: "For a VSF stack to support nonstop switching and routing, the stack must contain at least two members: one active and one standby." This directly supports answer B, as nonstop routing is achieved via Graceful Restart during a failover.

2. ArubaOS-CX 10.12 OSPF Guide, Page 13, Section: "Graceful restart support".

Quote: "Helper mode: Supported on all platforms." This confirms that the ArubaOS-CX 6100 series supports the GR helper role, validating answer A.

3. ArubaOS-CX 10.12 OSPF Guide, Page 15, Section: "OSPF graceful restart and BFD interaction".

Quote: "When both OSPF graceful restart and BFD are enabled on an interface, if the BFD session goes down, it will not wait for the graceful restart timer to expire and will bring down the OSPF neighbor relationship immediately." This shows the features are not mutually exclusive, invalidating answer C.

4. RFC 3623: Graceful OSPF Restart, Section 2.3, "The Grace-LSA".

Reference: This RFC specifies that the restarting router originates the Grace-LSA, and helper routers must recognize and process it. This highlights the imprecision in statement D, which generalizes that all "OSPF Routers listen".