A management network allows administrators to remotely access all switches on the network for configuring, managing, and analyzing traffic. This prevents having to be physically present at each switch in order to manage it. There are two prevalent approaches for network management: In-band and out-of-band (OOB). An introduction to in-band and out-of-band network management approaches is covered in this chapter.
The method used for management should be carefully considered when designing a network. Switches that use in-band management may become inaccessible if parts of the network are down, but can take advantage of security features such as those provided by access control lists, or ACLs.
A management switch is not required for in-band in order for a management station to achieve one-to-many access of the switches. Administrators can create a tier or daisy-chain network using the management VLAN (requiring two management ports on middle switches).
On any in-band management network, in-band management is lost when a switch goes offline due to wrong configurations, power-cycling, or cable disconnections. In these cases, the administrator can no longer reach affected devices to determine or resolve issues over the network. Until resolved, the serial port on the switch must be used to recover the switch. Extended downtime is often required to access the serial port to restore the switch. SNMP traps, external logging, and other alerts/notifications may also be missed when a switch suddenly goes offline causing further delays in recognition and recovery.
While OOB management typically requires dedicated switching and cabling, it provides an alternate path to circumvent the problems of in-band management. When a switch goes offline due to misconfiguration or a cable disconnect, the OOB management connection remains up. Network administrators are notified immediately through SNMP traps and alerts, and may begin troubleshooting and recovery efforts.