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Link flaps occur on VDX2746 with Nexus 3524(N3K-C3524P-10G)

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TitleLink flaps occur on VDX2746 with Nexus 3524(N3K-C3524P-10G)
Link flap seen between Nexus 3K and VDX 2746
The issue might not been seen with older release such as VDX 2746 NOS 4.0.1_hit1
The issue is seen after upgrading to NOS 6 due to recent behaviorchanges of link negotiation and Fabric discovery capability.
The issue might not be seen with some Cisco platforms such as Nexus 5K as they ignore the BLD frames which they do understand but issue momentary link flap would be seen when VDX peers with Cisco Nexus 3K.
Software Release: NOS6.0.0
Fixed in Version: N/A
  • During the neighbor discovery stage the BLDP(Brocade Link Discovery Protocol) uses LR/LRR signalling (Link reset/ Link reset request)
  • The LR/LRR signalling is a proprietary mechanism to detect Brocade partner on the other end andestablish ISL capabilities
  • The discovery protocol is implemented as mac layer Brocade proprietary and its objective is to detect if the adjacent switch is VCS capable or not
  • It is recommended the discovery protocolbe executed only if we are connecting a Brocade switch.
For the flapping interface which peers with Cisco Nexus devices:

conf t
interface x/y
fabric neighbor-discovery disable

Please note: This command will only take effect on shut/no shut of the related interface or reboot of the switch.
Overall the Cisco Nexus 3K is not able to understand the LR/LRR frames and causes the link to flap,
Disabling the fabric discovery causes the link flaps issue to be resolved.
Additional notes



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