JUEX-L2-000100 - The Juniper EX switch must be configured to enable STP Loop Protection on all non-designated STP switch ports.

Information

The Spanning Tree Protocol (STP) Loop Protection feature provides additional protection against STP loops. An STP loop is created when an STP blocking port in a redundant topology erroneously transitions to the forwarding state. In its operation, STP relies on continuous reception and transmission of BPDUs based on the port role. The designated port transmits BPDUs, and the non-designated port receives BPDUs. When one of the ports in a physically redundant topology no longer receives BPDUs, the STP conceives that the topology is loop free. Eventually, the blocking port from the alternate or backup port becomes a designated port and moves to a forwarding state. This situation creates a loop. The loop protection feature makes additional checks. If BPDUs are not received on a non-designated port and loop protection is enabled, that port is moved into the STP loop-inconsistent blocking state.

NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.

Solution

Configure the switch to have STP Loop Protection enabled on all non-designated STP interfaces.

RSTP or VSTP non-designated interface loop protection:
set protocols rstp interface <interface name> bpdu-timeout-action block
set protocols vstp interface <interface name> bpdu-timeout-action block

All instances on an MSTP interface:
set protocols mstp interface <interface name> bpdu-timeout-action block

Note: Loop Protection and Root Protection are mutually exclusive and cannot be simultaneously configured on the same interface.

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_Juniper_EX_Switches_Y24M07_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-5, CAT|II, CCI|CCI-002385, Rule-ID|SV-253957r843904_rule, STIG-ID|JUEX-L2-000100, Vuln-ID|V-253957

Plugin: Juniper

Control ID: 4d46bc2c5644ba406cca1896d507d73009b09762d7a8db0524a3da23b142779c