Lync Common Area Phones Won’t Automatically Login

I’ve encountered this one twice now, so I figure it’s worthy of a post.


  • Your new Lync deployment looks good
  • DhcpUtil.exe –EmulateClient works like a charm, reporting SUCCESS
  • You plug a new Common Area phone in and jump through the config settings on screen. It logs in OK
  • Choose either :
    • You move it to its new location and plug it in
    • You leave it alone, it sucks a firmware update and automatically reboots
  • You expect the phone will login, but instead you get this error:
    “Certificate web service cannot be found. Please contact your support team”. [Wonderful: that’s me!]
  • BUT: if you now re-key the phone number and PIN, it will login OK.

The fix is a simple one: you have Spanning Tree enabled, and the phone times out its DHCP discovery and initialisation process while the port is still in a listening/learning state. (That’s why if you re-key the number and PIN it will login OK).

The fix is to reconfigure the switch to enable PortFast.

(Reference – and a shout out to Eric for the tipoff).

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