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Cisco Bug: CSCur01785 - N5K VPC+: FEX drops unknown unicast packet

Last Modified

Sep 09, 2019

Products (7)

  • Cisco Nexus 5000 Series Switches
  • Cisco Nexus 5596UP Switch
  • Cisco Nexus 5548P Switch
  • Cisco Nexus 6004 Switch
  • Cisco Nexus 6001 Switch
  • Cisco Nexus 5548UP Switch
  • Cisco Nexus 5596T Switch

Known Affected Releases

6.0(2)N2(1) 6.0(2)N2(5) 7.0(3)N1(0.99)

Description (partial)

unknown unicast packets are dropped in FEX(N2248 TP-E).

This issue can heppen when N5K meets these situation.
 - Using Fabric-Path
 - Using Dual-Homed FEX
 - Secondary VPC Peer is forwarding the packet to FEX.
 - N5Ks doesn't know MAC address of destination.


 N7K -----+
  |       |  FP NETWORK BETWEEN N7K and N5K
  |       |
 N5K === N5K (VPC+)
  |       |
  |       |
 N2K -----+ (Dual Home)
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