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Cisco Bug: CSCvi11291 - XR L3 learn on BL even with "Disabled remote EP learn" enabled given a pkt with src/dst port of 179

Last Modified

Aug 13, 2019

Products (22)

  • Cisco Nexus 9000 Series Switches
  • Cisco Nexus 9516 Switch
  • Cisco Nexus 9396PX Switch
  • Cisco Nexus 9396TX Switch
  • Cisco Nexus 93108TC-FX Switch
  • Cisco Nexus 93120TX Switch
  • Cisco Nexus 9504 Switch
  • Cisco Nexus 93108TC-EX Switch
  • Cisco Nexus 9372TX-E Switch
  • Cisco Nexus 9508 Switch
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Known Affected Releases

12.3(1h) 13.1(2m) 13.1(2o) 13.1(2p)

Description (partial)

XR IP learning occurs on border leaf switches even when 'disabled remote EP learn' is configured for the fabric. XR IP learns should only occur on border leaf switches for routed multicast packets with PIM enabled.

Example of frame from an EP:

Internet Protocol Version 4, Src:, Dst:
Transmission Control Protocol, Src Port: 179, Dst Port: 46839, Seq: 1, Ack: 1, Len: 0

When this packet arrives from compute leaf to Border leaf, it triggers XR IP learn pointing towards compute leaf.

this is not always a problem, however if the the EP moves to a different compute leaf, the XR IP is not updated until the similar frame triggers the learn again. which causes outage for the EP as it becomes unreachable for external networks.
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