Out-of-band management

Out-of-band management is remote control of a server through a separate controller that runs independently of the host operating system. That controller is the baseboard management controller (BMC). The DMTF describes it as an independent microprocessor or system-on-chip with its own firmware that handles out-of-band monitoring and management. It has its own network connection, so an admin can reach it when the OS has crashed. In-band management goes through the host OS and stops with it.

Each vendor brands its BMC. Dell calls it iDRAC, HPE calls it iLO, and Lenovo calls it the XClarity Controller, or XCC, which replaces the BMC on ThinkSystem servers. Dell's security guide recommends setting iDRAC NIC Select to Dedicated, so management uses its own port. Lenovo offers a dedicated or shared Ethernet connection, and some ThinkSystem models have no dedicated port at all. On the XCC, REST over HTTPS uses port 443 and IPMI over LAN uses port 623, both fixed. SSH defaults to port 22.

Specify a dedicated management port, not a shared one. Put it on an isolated network or VLAN, and disable IPMI over LAN if nothing uses it.

Sources

Last verified October 30, 2026.