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[EX] Protocols for IPV4 delayed when entering ingress through a backup member in EX4300



Article ID: KB32976 KB Last Updated: 03 Apr 2021Version: 3.0

This article explains why a delay or latency may be noticed when traffic enters ingress through a backup member of an aggregate interface in the EX4300 Series of devices.

Note: This issue is only for traffic that is destined to the Routing Engine (RE) and not applicable to transit traffic. It is applicable to IPV4 and not IPV6.



When traffic enters ingress through a backup member aggregate link, latency or delay might be noticed for protocols such as Internet Control Message Protocol (ICMP) or Secure Shell (SSH).

    irb.10:          +-----------------------+        |                       |ge-0/0/0(AE0)
+--------------------+-+                     |
|     EX4300(FPC1)MRE  |                 +---+----+
+----------------------+                 | EX4200 +----------> Host
|     EX4300(FPC0)BRE  |                 +---+----+        (
+--------------------+-+                     |
                     |                       |ge-0/0/1(AE0)

root@EX4300-VC> show virtual-chassis status
Virtual Chassis ID: 5fb8.939a.c82f
Virtual Chassis Mode: Mixed

                                                Mstr           Mixed Route Neighbor List
Member ID  Status   Serial No    Model prio  Role      Mode  Mode ID  Interface
0 (FPC 0)  Prsnt    PE3717130104 ex4300-48t     250   Backup       VC   1  vcp-255/1/0                                                                         
1 (FPC 1)  Prsnt    PE3717130438 ex4300-48t     255   Master       VC   0  vcp-255/1/0
EX4300-VC> ping count 10
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=64 time=195.077 ms
64 bytes from icmp_seq=1 ttl=64 time=4.237 ms
64 bytes from icmp_seq=2 ttl=64 time=11.119 ms
64 bytes from icmp_seq=3 ttl=64 time=285.382 ms
64 bytes from icmp_seq=4 ttl=64 time=47.039 ms
64 bytes from icmp_seq=5 ttl=64 time=155.161 ms
64 bytes from icmp_seq=6 ttl=64 time=11.318 ms
64 bytes from icmp_seq=7 ttl=64 time=10.388 ms
64 bytes from icmp_seq=8 ttl=64 time=294.514 ms
64 bytes from icmp_seq=9 ttl=64 time=56.558 ms

--- ping statistics ---
10 packets transmitted, 10 packets received, 0% packet loss
round-trip min/avg/max/stddev = 4.237/107.079/294.514/110.200 ms



This is because the switch is configured for mixed-mode virtual-chassis, even though a same-mode virtual-chassis exists in the EX4300 Series of devices.

The aggregate link is configured on a virtual-chassis where child interfaces are present on both the primary and the backup member.


To avoid the delay, switch from mixed mode to normal mode by using the following command:

user@switch> request virtual-chassis mode mixed disable all-members

Reboot all member switches in the virtual chassis to complete the preceding step:

user@switch> request system reboot all-members
Modification History:

2018-08-20: Corrections made to Topology in Solution section to be valid with log output
2021-03-25: Updated the article terminology to align with Juniper's Inclusion & Diversity initiatives.



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