Medianet Reference Guide - Cisco

Chapter 3
Medianet Availability Design Considerations
Summary
• Object-tracking events
• Online insertion and removal events
• Resource events
• GOLD events
• Redundancy events
• Simple Network Management Protocol (SNMP) events
• Syslog events
• System manager/system monitor events
• IOS watchdog events
• Timer events
Capturing the state of network devices during such situations can be helpful in taking immediate
recovery actions and gathering information to perform root-cause analysis, reducing fault detection and
diagnosis time. Notification times are reduced by having the device send e-mail alerts to network
administrators. Furthermore, availability is also improved if automatic recovery actions are performed
without the need to fully reboot the device.
Cisco In Service Software Upgrade
Cisco ISSU provides a mechanism to perform software upgrades and downgrades without taking a
switch out of service. ISSU leverages the capabilities of NSF and SSO to allow the switch to forward
traffic during supervisor IOS upgrade (or downgrade). With ISSU, the network does not re-route and no
active links are taken out of service. ISSU thereby expedites software upgrade operations.
Online Insertion and Removal
OIR allows line cards to be added to a device without affecting the system. Additionally, with OIR, line
cards can be exchanged without losing the configuration. OIR thus expedites hardware repair and/or
replacement operations.
Summary
Availability was shown to be a factor of two components: the mean time between failures (MTBF) and
the mean time to repair (MTTR) such failures. Availability can be improved by increasing MTBF (which
is primarily a function of device and network resiliency/redundancy), or by reducing MTTR (which is
primarily a function of operational resiliency.
Device availability technologies were discussed, including Cisco Catalyst StackWise/StackWise Plus
technologies, which provide 1:N control plane redundancy to Cisco Catalyst 3750G/3750E switches, as
well as NSF with SSO, which similarly provides hot standby redundancy to network devices with
multiple route processors.
Network availability technologies were also discussed, beginning with Layer 2 technologies, such as
spanning tree protocols, trunking protocols, EtherChannel protocols, and Cisco VSS. Additionally,
Layer 3 technologies, such as HSRP, VRRP, GLBP, and IP Event dampening were introduced.
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Medianet Reference Guide
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