This article addresses a minor alarm observed on an MX480 router involving FPC2, where log messages indicate memory partition alignment issues along with critically low Next Hop (NH) and Firewall (FW) memory. This can affect inline services and flow monitoring performance if left unchecked.

Minor alarm on FPC 2

System log shows:

fpc2 jnh_physmem_add_to_partition(17615): PFE 3 RESERVED 0x001c0000 @ 0x00940000 !FREE and ! 1M aligned.

Heap memory utilization on FPC2 drops below safe threshold (e.g., 22% free)

NH and FW memory show 4% free with watermark exceeded

show system resource-monitor fpc confirms memory pressure on FPC2:

• Heap Free: 22%
• NH and FW memory across all PFEs on FPC2: 4%* (* indicates threshold crossed)

Compared to healthy FPCs (e.g., FPC 0 and 5 with 70–96% free memory)

Inline-jflow configuration and flow-table sizes appear nominal:

• IPv4/IPv6 flow-table-size: 4
• Sampling rate: 4096 (acceptable)

Traceoptions may be contributing to unnecessary memory pressure

Perform the following steps during a maintenance window:

1. Disable Traceoptions (if enabled):

delete services flow-monitoring inline-jflow sampling-instance <INSTANCE-NAME> traceoptions

2. Enable Extended Flow Memory on FPC2 PFEs:

set services flow-monitoring inline-jflow fpc-slot 2 pfe 0 extended-flow-memory

set services flow-monitoring inline-jflow fpc-slot 2 pfe 1 extended-flow-memory

set services flow-monitoring inline-jflow fpc-slot 2 pfe 2 extended-flow-memory

set services flow-monitoring inline-jflow fpc-slot 2 pfe 3 extended-flow-memory

commit

This allows the system to utilize more memory for flow-based features.

Reference: https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/statement/use-extended-flow-memory-edit-chassis.html