Management Networks

In-band and Out-of-Band management traffic is related to Management plane. There are two main ways to manage a network: In-band and Out-of-band (OOB).
In-band refers to managing through the network itself, usually dedicated vlan, as separation from production environment. Telnet/SSH protocols could be used to connect to environment or using SNMP-based tools.
For large or business-critical networks, in-band network management is not enough. If the network is down, reachability to network device is affected and this is a big risk for the organization and its business.
You need an alternate or secondary access path to get around the problem or to access the source of the problem – that is essentially what Out-of-Band Management (OOB) provides.