Which two characteristics apply to Cisco Catalyst 6500 Series Switch supervisor redundancy
using NSF? (Choose two.)
A.
supported by RIPv2, OSPF, IS-IS, and EIGRP
B.
uses the FIB table
C.
supports IPv4 and IPv6 multicast
D.
prevents route flapping
E.
independent of SSO
F.
NSF combined with SSO enables supervisor engine load balancing
Explanation:
A key element of NSF is packet forwarding. In a Cisco networking device, packet forwarding is
provided by Cisco Express Forwarding (CEF). CEF maintains the FIB, and uses the FIB
information that was current at the time of the switchover to continue forwarding packets during a
switchover. This feature reduces traffic interruption during the switchover.
During normal NSF operation, CEF on the active supervisor engine synchronizes its current FIB
and adjacency databases with the FIB and adjacency databases on the redundant supervisor
engine. Upon switchover of the active supervisor engine, the redundant supervisor engine initially
has FIB and adjacency databases that are mirror images of those that were current on the active
supervisor engine. For platforms with intelligent modules, the modules will maintain the current
forwarding information over a switchover. For platforms with forwarding engines, CEF will keep the
forwarding engine on the redundant supervisor engine current with changes that are sent to it by
CEF on the active supervisor engine. The modules or forwarding engines will be able to continue
forwarding after a switchover as soon as the interfaces and a data path are available.
As the routing protocols start to repopulate the RIB on a prefix-by-prefix basis, the updates will
cause prefix-by-prefix updates to CEF, which it uses to update the FIB and adjacency databases.
Existing and new entries will receive the new version (“epoch”) number, indicating that they have
been refreshed. The forwarding information is updated on the modules or forwarding engine
during convergence. The supervisor engine signals when the RIB has converged. The software
removes all FIB and adjacency entries that have an epoch older than the current switchover
epoch. The FIB now represents the newest routing protocol forwarding information.