Symptom
- Line protocol of a physical interface is frequently flapping.
- Link (L1) is always up: HundredGigE2/0/9 is up (always UP), line protocol is (changing between DOWN & UP)
- For L2 trunk ports, if a L3 neigborship is build on top of the SVIs, it will cause adjacency instability, i.e.:
%LINEPROTO-5-UPDOWN: Line protocol on Interface HundredGigEx/x/x, changed state to down
%PIM-5-NBRCHG: neighbor x.x.x.x DOWN on interface Vlanxxxx non DR
%OSPF-5-ADJCHG: Process 10, Nbr x.x.x.x on Vlanxxxx from FULL to DOWN, Neighbor Down: Interface down or detached
%OSPF-5-ADJCHG: Process 3, Nbr x.x.x.x on Vlanyyyy from FULL to DOWN, Neighbor Down: Interface down or detached
%OSPF-5-ADJCHG: Process 6, Nbr x.x.x.x on Vlanzzzz from FULL to DOWN, Neighbor Down: Interface down or detached
Conditions
Chassis: C9606R
IOS-XE version: 17.9.1
Line card: C9600-LC-24C
Supervisor in use: C9600X-SUP-2
SPFs in use: QSFP-40G-SR-BD
Note(s): This has been noticed when the neighbor device is a Nexus switch, i.e.: C9336C-FX2. This issue has been reported on C9600 switches running with C9600X-SUP-2.
Workaround
No workaround(s) at this point.
