The request came from a peer the receiving node doesn't know (DIAMETER_UNKNOWN_PEER).
Where you see it
In the Result-Code or Experimental-Result-Code AVP of a Diameter answer (S6a, S6d, Gx, Gy, Cx…).
What to check
Check the peer configuration (Origin-Host, realm, allowed peers) on the node that answered.
Look at the Origin-Host of the answer: an intermediate agent (DRA/IPX) and the home HSS mean different owners of the problem.
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