The Nokia multicast Designated Router (DR) must be configured to increase the shortest-path tree (SPT) threshold or set it to infinity to minimize source-group (S, G) state within the multicast topology where Any Source Multicast (ASM) is deployed.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-283858 | NOKI-RT-000400 | SV-283858r1203823_rule | CCI-002385 | medium |
| Description | ||||
| SM can have many sources for the same groups (many-to-many). For many receivers, the path via the Rendezvous Point (RP) may not be ideal compared with the shortest path from the source to the receiver. By default, the last-hop router will initiate a switch from the shared tree to a source-specific SPT to obtain lower latencies. This is accomplished by the last-hop router sending a source-group Protocol Independent Multicast (PIM) Join toward S (the source). When the last-hop router begins to receive traffic for the group from the source via the SPT, it will send a PIM Prune message to the RP for the source group. The RP will then send a Prune message toward the source. The SPT switchover becomes a scaling issue for large multicast topologies that have many receivers and sources for many groups because source-group entries require more memory than (*, G). Hence, it is imperative to minimize the amount of source-group state to be maintained by increasing the threshold that determines when the SPT switchover occurs. | ||||
| STIG | Date | |||
| Nokia Service Router OS 25.x Router Security Technical Implementation Guide | 2026-06-15 | |||
Details
Check Text (C-283858r1203823_chk)
Review the multicast last-hop router configuration to verify the SPT switchover threshold is increased (default is "0") or set to infinity (never switch over).
Use the command below to verify the "Spt threshold" value:
- show router pim group detail | match "Spt threshold"
Spt threshold : 4294967295 kbps ECMP opt threshold : 7
If any multicast router is not configured to increase the SPT threshold or set to infinity to minimize source-group state, this is a finding.
Fix Text (F-88328r1203822_fix)
Configure the multicast router to increase the SPT threshold or set it to infinity to minimize the source-group state within the multicast topology where ASM is deployed, as shown in the example below:
- configure router pim spt-switchover-threshold 239.4.4.0/24 "infinity"