Description

  • With the following topology when router B sends a ping with 1200 byte, we expect that EX4100-F sends a ICMP Type 3, Code 4 but it doesn't.
  • This causes a problem which Path MTU Discovery is not triggered.
  • Router A --- (ge-0/0/8, MTU 1000) EX4100-F (ge-0/0/12, MTU 9001) --- Router B <---------- ping with 1200 byte
  • Customer has EX4100 to IOT devices. Whenever one IoT device tries to reach other device with packet size greater that than the MTU size on the interface ICMP type 3 code 4 is not getting generated.

 

Solution

  • Engineering team has identified a hardware limitation at BCM chipset design. Unfortunately this limitation can not resolved through software fixes or update.
  • The issue is that high MTU packets are being dropped in BCM, the should be sent to CPU via register settings but that is not happening as due to design issue with Broadcom chipset. 

Modification History

2024-05-02 : Article Created

2026-10-01 : Externalized