Description

fast-lookup-filters FLT filters do not work for vxlan packets and might result in packet drops

Symptoms

Following pfe errors are seen on the FPC/PFE and vxlan packet will get dropped when FLT filters are enabled on MX platforms using


set routing-options flow fast-lookup-filter


Apr 18 08:24:45 MX240-JTAC-LAB fpc0 ppe_error_interrupt(5538): EA[0:0]_PPE 49 Errors sync xtxn error

Apr 18 08:24:45 MX240-JTAC-LAB fpc0 ppe_error_interrupt(5538): EA[0:0]_PPE 24 Errors sync xtxn error

Apr 18 08:24:45 MX240-JTAC-LAB fpc0 ppe_error_interrupt(5538): EA[0:0]_PPE 25 Errors sync xtxn error

Apr 18 08:24:45 MX240-JTAC-LAB fpc0 ppe_error_interrupt(5538): EA[0:0]_PPE 0 Errors sync xtxn error

Apr 18 08:24:46 MX240-JTAC-LAB fpc0 filter_xif_event_handler(5566): EA[0:0].filter XIF XTXN_SZ_ERROR 0x0000000f

Solution

With VXLAN enabled on MX device, device should be explicitly configured in loopback mode for fast-lookup-filters to work for VXLAN packets. Currently this is limitation with default optimize mode so we need to change to loopback mode.

 

The following knob is required to change VXLAN default optimize mode to loopback mode. 

 

set chassis loopback-dynamic-tunnel

 

In addition, chassis reboot is required for this knob to take effect.

Modification History

2026-07-31 : Article Created