F5 hashing method to store user passwords - what is it?

Hi,

Question: What is the F5 hashing method used for user-password encryption?

I want to convert any given plain-text string to F5-compliant 34-byte password hash (used by TMOS to store encrypted user passwords as seen below):

auth user fred {
        description "fred"
        encrypted-password "$1$7bJKKtIK$QtBoSymfzhuJcyjOTiJlz0"
        partition Common
        partition-access all
        role admin
        shell bash
}

• It must be doable on a non-F5 box, e.g regular Linux machine. I want to avoid doing the initial conversion on F5 box for automation purpose.
• Seems like some sort of MD5, but not the regular 32-byte version of MD5 as the total length is 34. Also the first 3 symbols of prefix appear to be static

  $1$

  . Can anyone identify this format, or link to relevant documentation?