Which three fields are optional in an OSPFv3 external LSA？（）

A. The trunking configuration mode on Switch1 is set to Off.
B. The trunking configuration mode on the other end is set to On.
C. The trunking configuration mode on the other end is set to Desirable.
D. Cisco Discovery Protocol is not running on the other end.
E. There is a VTP domain name mismatch.
F. Switch1 does not support 802.1Q

A.It allows the standby RP to take control of the device after a hardware or software fault on the active RP.
B.It is a Layer 3 function that works with SSO to minimize the amount of time a network is unavailable tousers following a switchover.
C.It is supported by the implementation of EIGRP， OSPF， RIPv2， and BGP protocols.
D.It synchronizes startup configuration， startup variables， and running configuration.
E.The main objective of NSF is to continue forwarding IP packets following a switchover.
F.Layer 2 802.1w or 802.1s must be used， as 802.1d cannot process the Layer 2 changes.
G.Routing protocol tuning parameters must be the same as the NSF parameters， or failover will beinconsistent.

A. The VSS switch must be the root bridge for all VLANs and is automatically designated
B. The VSS switch is defined in RFC 4318 as a managed object
C. The PAgP+ or LACP protocols are used to maintain the operational state of the VSS devices
D. A VSS interoperates with a virtual port channel
E. The 802.1Q or ISL protocols are used to maintain the operational state of the VSS devices
F. A VSS increases the size of the spanning-tree domain