I have a dream... that after memorizing one 2-octave fingering, you will be able to play any major (=ionian)/dorian/phrygian/lydian/mixolydian/minor (=aeolian) and locrian scale anywhere on your neck. That's 7*12=84 scales total!!!

Here's what you do:

chances are, you're already familiar with this "standard" major scale fingering, which starts on your 2nd finger (and, btw, ends on your 4th finger):

HOWEVER... that only let's you play your C-major scale in 3 different places on your neck. You can dramatically increase your "coverage" (actually to 100%) by also memorizing this fingering, starting on your 4th finger (and, btw, ending on your 2nd finger!! also note the little "shift" between your 5th and 6th scale degree - this is very important!!):

And here's the punch line: now that you know that the fingering starting on your 2nd finger ends on your 4th finger, and the one starting on your 4th finger ends on your 2nd finger, it is a "no brainer" to combine those two to create one 2-octave fingering.
Played across 5 strings, if you start on your 2nd finger, after covering one octave you can continue using your 4th finger version:

Note that the notes I whistled would complete the 2-octave fingering if I only had a 6 string bass. In that case I would end on my starting finger (2nd finger in that case), only 2 octaves higher and one fret lower (thanks to the little shift between 5th and 6th scale degree during your second octave). And considering that a 6 string bass has a B as your lowest, and a C as your highest string, you must end up one fret lower ;-).

Now, likewise, if you start on your 4th finger, you can continue with your 2nd finger version after one octave:

Note that again, the notes I whistled would complete the 2 octave fingering and let you arrive on your starting note with your starting (i.e. 4th) finger, only 2 octaves higher and one fret lower. See a pattern / divine system here???
If you had a bass with an infinite number of strings (thank God you don't!!), you could continue playing that 2 octave fingering until you make your dog scream (past 16 kHz or so), moving one fret lower every 2 octaves (compliments of Mr. Pythagoras)...

So, how can I put the system to work? Here's C major all across the neck (excluding open strings), ascending:

And descending:

Remember I promised you can use that very same 2-octave fingering to play any major scale (and all the "modes" that are based on it) - here's D major all across the neck. For demonstrative purposes, I pause briefly everytime I reach my "root" note (D in that case). Note that all those "roots" are either played with my 2nd or 4th finger:

And without pausing on roots:

Convinced? I hope so. This "system" was inspired by Gary Willis' use of "2nd-" and "4th-finger diatonic" as in his great book "Fingerboard Harmony for Bass".