# istio_29427.yaml
apiVersion: release-notes/v2
kind: bug-fix
area: networking
issue:
  - 29427
  - 28516
upgradeNotes:
  - title: Connectivity issues among your proxies when updating from 1.7.x to 1.7.5 or newer.
    content: |
      When upgrading your Istio data plane from 1.7.x (where x < 5) to 1.7.5 or newer, you may 
      observe connectivity issues between your gateway and your sidecars or among your sidecars 
      with 503 errors in the log. This happens when 1.7.5+ proxies send HTTP 1xx or 204 response 
      codes with headers that 1.7.x proxies reject. To fix this, upgrade all your 
      proxies (gateways and sidecars) to 1.7.5+ as soon as possible.