Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860/CP920 IP Phones 
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Incoming Signaling Validation 
Yealink IP phones support the following three optional levels of security for validating incoming 
network signaling: 
  Source IP address validation: ensure request is received from an IP address of a server 
belonging to the set of target SIP servers. 
  Digest authentication: challenge requests with digest authentication using the local 
credentials for the associated registered account. 
  Source IP address validation and digest authentication: apply both of the above methods. 
Procedure 
Incoming signaling validation can be configured using the configuration files. 
Configure incoming dignaling 
validation. 
Parameter: 
sip.request_validation.source.list 
sip.request_validation.digest.list 
sip.request_validation.digest.realm 
sip.request_validation.digest.event