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Cisco Bug: CSCut65950 - Border leaf iBGP route flapping when it loses all its external links

Last Modified

Jul 26, 2017

Products (1)

  • Cisco LAN Switch Software

Known Affected Releases

11.0(3g)

Description (partial)

Symptom:
When border leaf BL201 loses both its links to external CI1 and CI2 (shut down from CIx side), we observed on BL1 that the the OSPF converges but the BGP route for external destination 0.0.0.0/0 was flapping between next hop of 10.64.8.82 (BL202 overlay-1/VTEP IP) and 10.6.126.1 and .2 (looked like due to recursive lookup for 10.6.126.1 and .2), and blackholing egress traffic for up to 180 seconds until BGP peering with CI1 and CI2 times out and route converges and back to stable condition.

Conditions:
iBGP is configured for L3-Out connection and border leaf loses all its external connections.
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