Using Simple Loop Prevention Protocol (SLPP)
Guard
Simple Loop Prevention Protocol (SLPP) is an application that detects loops in
an MLAG or Split Multi-link Trunking (SMLT) network on
VOSS/BOSS switches.
SLPP Guard is a complementary feature for ExtremeXOS switches that helps prevent loops
in networks by administratively disabling an edge port if a switch receiveS an SLPP PDU
from an SMLT network. SLPP Guard detects and discards SLPP control PDUs on a per port
basis. SLPP Guard identifies SLPP PDUs using the Ethernet type field of the packet,
which is configurable. When an SLPP PDU is received on a port that has SLPP Guard
activated on it, it is immediately disabled. After a configurable timeout value expires
(associated with each port), the port is automatically re-enabled.
Note
When SLPP Guard disables a port, the
disabled status is not persistent. If the switch reboots, the port is enabled when
the switch comes back up.
Note
If you use the CLI to enable or disable a port that has been disabled by SLPP
Guard, the port is enabled or disabled as applicable and the recovery timer is
stopped for that port.
The most common use case is with an IP phone with two ports: one for a switch
and one for a computer (see SLPP Use Case).
If you plug both IP phone ports onto the edge switch, a loop is created. To avoid a loop
in the SMLT network, on the ExtremeXOS edge switch, enable SLPP Guard on
the ports that are connected to the IP phone.
