ELRP (Extreme Loop Recovery Protocol) is a simple loop protection mechanism that sends a multicast packet out each configured port and checks to see if it receives it back on any port. If the packet is received back by the same switch, the port can be disabled, or the switch can notify via logs, SNMP traps, or both.
When ELRP disables a port, it can be disabled permanently, or for a set period of time. After the specified duration, the port will be re-enabled and the port will pass traffic while ELRP checks to see if the loop is still present. If this loop persists, the port will be disabled again.
ELRP should be configured not to disable uplink ports, so that ELRP will not disable the uplinks from a switch causing the switch to lose network connectivity.
ELRP can also be run in one-shot mode for detecting loops, even if it is not being used for loop protection.