Description

On mc-lag topology, short term duplicate BUM(Broadcast, Unknown unicast, Multicast) traffic would be seen when ICL link comes up. This is a current limitation and this KB describes the details.

Symptoms

Topology:
KB84880.png

MC-lag is configured on QFX#1 and QFX#2. While traffic generator#1, #2 and #3 are generating BUM traffic, BUM traffic is always flooding to ICL from QFX#1 and QFX#2.
In this topology, when ICL link between QFX#1 and QFX#2 comes up from down state, BUM packets duplication would be seen for shorter duration. This behavior could be seen regardless of whether comes up one child interface or all child interfaces configured as ICL. BUM duplication will recover on its own in shortly.

Solution

This is a limitation which is coming from internal process where programming internal filter and interface up. Both processes are carried out simultaneously and could bring the BUM duplication if re-enabling the interface is faster than programming internal filter to block BUM traffic.

Modification History

2024-08-014 : Added QFX5120-48T in AFFECTED PRODUCT SERIES.
2024-08-01 : Article Created