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Cisco Bug: CSCvv25887 - Port created via traffic w/o inventory blocks epp download

Last Modified

Oct 01, 2020

Products (1)

  • Cisco Application Policy Infrastructure Controller (APIC)

Known Affected Releases

2.2(3a)

Description (partial)

Symptom:
- On AVE VM A's port is stuck in the WAIT_ATTACH_ACK for a long period of time (15 mins up to multiple hours)
- The VM port is created/brought up due to dataplane traffic prior to inventory download from the attached ESXi host's Leafs
- When another VM - VM B - with port is brought up on the same AVE VM/ESXi host in the same PortGroup ... its port will be stuck in a WAIT_EPP state because VM-A's port is still pending inventory download to the Leaf and onto the AVE
- After a long time the inventory info for the ports is downloaded onto the Leafs and pushed to the AVE VM at which points the ports transition to a FWD state

Conditions:
Issue Is caused by the following sequence of events:
1.	On AVE - VM port with MAC-A created/brought up via dataplane traffic. There is no EP inventory for MAC-A in Datapath Agent (DPA).
2.	AVE sends PORT-ATTACH-REQ to Leaf with the download EPP (dldEpp) flag enabled for the PortGroup of the new VM port (step 1).
3.	Leaf does not have inventory for MAC-A, thus responds with an PORT-ATTACH-RETRY message via OpFlex. The dldEpp request is ignored.
4.	AVE re-sends PORT-ATTACH-REQ after a short wait. Leaf again sends PORT-ATTACH-RETRY msg via OpFlex.  Steps 2-3 repeat multiple times...
5.	During these retries, inventory for another EP with MAC-B is downloaded to AVE. MAC-B uses the same portgroup as MAC-A.
6.	AVE brings up VM port with MAC-B.  It sends PORT-ATTACH-REQ without the dldEpp flag since MAC-A already requested the same EPP.
7.	Leaf sends PORT-ATTACH-ACK for MAC-B.  AVE transitions VM port with MAC-B to a WAIT_EPP state.
8.	VM port for MAC-B is stuck in a WAIT_EPP state since the Leaf still can't process the dldEpp request due to MAC-A not being in its inventory.
9.	Eventually, inventory for MAC-A is downloaded to the Leaf and it processes the dldEpp request. 
10.	EPP is pushed to AVE and the VM port with MAC-A transitions to a forwarding state. Same happens to VM port with MAC-B after.
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