Answer
The comma (,) is a special character in ASN.1 DN and requires an escape character, to use which is the backslash (\).
The UTF-8 encoded string should not have any of the following characters:
- A space or pound (#) character occurring at the beginning of the string
- A space character occurring at the end of the string
- The comma (,), plus (+), double quote (""), back slash(\), less than or left triangle bracket (<), greater than or right triangle bracket (>), or semi-colon (;)
If the comma (,) character needs to be escaped, then it should be prefixed by a backslash (\) (ASCII 92).
Junos OS supports printable strings such as the comma for delimiters. You cannot use reserved characters, and using names with an underscore (_) can potentially cause problems.
For more information, see Understanding Certificates and PKI