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IP fragmentation is not working for IRB interfaces under EVPN on MX304 router.

  • 1.  IP fragmentation is not working for IRB interfaces under EVPN on MX304 router.

    Posted 02-29-2024 09:37

    Hello Team!

    I noticed that IRB interfaces that are part of the EVPN fabric do not fragment IP packets in the egress direction. I found some mention of a similar issue in Software Releases under number PR1522896

    "On MX and EX9200 serial platforms, with EVPN configured and IRB interface enabled under EVPN routing-instance, packets transported via IRB interface might not be fragmented. In the end, there is traffic impact. The reason of this issue is that MTU feature is not correctly to take effect on egress PFE."

    At the same time, the PR says that the problem is solved in versions: junos:18.4R2-S5-J1 junos:20.4R3-S4-J3 junos:21.2R3-S3 junos:21.2R3-S4 junos:21.3R3-S2 junos:21.4 R3-S2 junos:22.1R3-S1 junos:22.2R3 junos:22.3R2 junos:22.4R1 junos:22.4R2

    I tried installing different versions of the software on my MX304 router, such as 23.2R1-S2, 22.2R3-S2 and 22.4R2-S2, but the problem was not solved. Is it possible that the problem is still relevant for MX304 routers?

    I have two MX routers on my network that act as Anycast GW: MX304 and MX10003. When traffic is routed through the MX10003 there is no problem. When traffic is routed through MX304 - ip-packet loss occurs with mtu greater than 1500 (For Example: ping -s 2000 <host> is not working)

    The current version of JunOS is 23.2R1-S2.

    Has anyone encountered this problem and is there a workaround?

    Valentine Artemenok