Specifications

CHAPTER 5

Implementing High Availability

Technology

Some of the technologies found in Cisco routers and Layer 3 switches enhance availability by providing routing continu-

ity, fast failure detection to trigger a failover, and fast routing convergence. These include:

n Cisco Nonstop Forwarding (NSF)

n Stateful Switchover (SSO)

n Stackwise technology on 3750 switches

n Virtual Switch System (VSS)

n Monitoring tools such as SNMP and Syslog

n IP Service Level Agreement (SLA)

Each of these technologies is discussed in later sections of this chapter.

Some other technological features that enhance availability include server load balancing, firewall stateful failover, and

fast routing convergence.

People

Although the “people” part of high availability is not usually under the control of the network engineer, it is an important

part of the equation. The following items should be considered:

n Staff work habits: Staff should pay attention to detail, and their work should be reliable and consistent to make

troubleshooting easier.

n Staff skills and technical training: A knowledgeable staff understands the network technologies and configures

devices correctly. A company lab enables failover scenarios to be tested before incorporating them into the network

and allows network engineers to practice their skills.

[ 60 ]

CCNP SWITCH 642-813 Quick Reference by Denise Donohue

9781587140112.qxd 11/23/09 11:35 AM Page 60