Aastra 53i Release Note page 34

IP Phone Release Notes 2.1
Security Features
Parameter –
sips root and intermediate
certificates
Root and Intermediate
Certificates
(in Web UI)
Description
Format
Default Value
Range
Example
28
Aastra Web UI
Configuration Files
Allows you to specify the SIP Root and Intermediate Certificate files to use
when the phone uses the TLS transport protocol to setup a call.
The Root and Intermediate Certificate files contain one root certificate and
zero or more intermediate certificates which must be placed in order of
certificate signing with root certificate being the first in the file. If the local
certificate is signed by some well known certificate authority, then that
authority provides the user with the Root and Intermediate Certificate files
(most likely just CA root certificate).
This parameter is required when configuring TLS (optional for Persistent
TLS.)
Note: The certificate files must use the format ".pem". To create custom
certificate files to use on your IP phone, contact Aastra Technical Support.
<file name>.pem
N/A
N/A
sips root and intermediate certificates: cacert_openser.pem
Advanced Settings->TLS Support
aastra.cfg, <mac>.cfg
RN-001029-00, Rev 03, Release 2.1