nx.os.and.cisco.nexus.switching.2nd.edition.1587143046

Other supervisor (sup-5)
------------------------
Redundancy state: Standby
Supervisor state:
Internal state:
HA standby
HA standby
System start time: Fri May 4 07:42:43 2012
System uptime:
128 days, 9 hours, 21 minutes,
1 seconds
Kernel uptime:
128 days, 9 hours, 25 minutes,
42 seconds
Active supervisor uptime: 0 days, 0 hours, 7 minutes, 39
seconds
Nonstop Forwarding
Most modern protocols understand that while a control plane switchover might be occurring
on an adjacent node, the data plane can still forward traffic. The most common
implementations of this functionality are with OSPF, EIGRP, and BGP. These mechanisms
are sometimes referred to as a graceful restart. This should not be confused with a stateless
restart; a stateful restart requires no interaction with peers, whereas a graceful restart
involves notification of peers.
If a stateful restart of the routing process fails, or is not possible, nonstop forwarding (NSF)
specifies a mechanism to notify neighbors that the control plane is undergoing a restart, but
the data plane can still forward traffic. All routing updates from this neighbor are held in
their current states until the adjacency is restored or a hold timer expires. When the
adjacency is reestablished, updates to the routing topology are then updated in the hardware
forwarding tables. For NSF to work properly, the adjacent network devices must process
the notification, in which case they are said to be NSF-Aware. Most modern networking
devices, including IOS and NX-OS, are NSF-Aware.
In-Service Software Upgrades
With the combination of the distributing forwarding nature of the Nexus platform and the
high-availability features described within this chapter, one of the most immediate and
practical benefits of the approach is the capability to upgrade software without requiring a
reload of the system or disruption to traffic flows through the system. This capability is
referred to as In-Service Software Upgrades (ISSU), which is supported across both minor
and major NX-OS versions and enables customers to quickly take advantage of new
features, protect their infrastructure against security vulnerabilities, and provide a more
proactive software upgrade cycle, all while not having to wait for extended maintenance
windows or costly downtime. Prior to initiating a software upgrade, an administrator should