Yealink SIP-T48G Administrator's Manual page 245

Configuring Security Features
4) Click Upload to upload the certificate.
d) If you select EAP-TTLS/EAP-MSCHAPv2:
1) Enter the user name for authentication in the Identity field.
2) Enter the password for authentication in the MD5 Password field.
3) In the CA Certificates field, click Browse to select the desired CA certificate
(*.pem, *.crt, *.cer or *.der) from your local system.
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