True, I forgot about that.
nano /etc/asterisk/sip_custom_post.conf
Insert
[101](+)
mohsuggest=Test
(Edit: I don’t recall if Chan_SIP also supports adding types in parentheses)
Reload:
[root@yplab ~]# asterisk -x"core reload"
[root@yplab ~]# asterisk -x"sip show peer 101" | grep MOH
MOH Suggest : Test