Github user swill commented on the issue: https://github.com/apache/cloudstack/pull/2003 I have to admit, I am not sure how the IP was found when looping through the list initially, but then when trying to update the index for the IP that was found, it is not there. The only way I can think of that would cause this is if the IP <-> dev mapping is broken somehow. It found the matching IP, but apparently that IP is not on the dev defined by the `nic_dev_id` (which comes from either: `nic_dev_id = address['nic_dev_id']` (from the databag), which can then be overridden by `nic_dev_id = ip['nic_dev_id']` (from the passed in IP) ). Yes, I think you are right that the `else` case does not work right now. This is because we are appending the IP to this dev, but we never removed it from the other dev it was apparently found in. This logic is SUPPOSED to find the existing IP's index and then if found, update that index with the updated info. The old logic which just removed all "found" IPs and then re-added them, did not preserve the order, so the source nat IP could get reconfigured as a secondary IP on a nic instead of it being primary. This reordering of the IPs on VR reboot caused the VPN to fail because the source nat IP was no longer the primary IP. So we know that removing all found IPs and then adding them does not work because it changes the order of the IPs causing the source nat IP to become a secondary IP on the nic. The error described in CLOUDSTACK-9811 seems to be a situation where the IP is found on one nic, but then for some reason the dev which the IP is associated with is changed (I don't know why this would be happening), causing the index where the IP was found to not be valid because the IP is actually on a different dev. To know how to fix this correctly, we need to understand why/how an IP can be associated with one dev (index found) and then get changed to be associated with a different dev. We need to find a way to preserve IP order while being able to update the IP configurations. @remibergsma do you have any ideas on this? Anyone else have ideas here?
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