Warning: Catholic answer to not specifically Catholic question ahead.
This passage in Genesis is known as the protoevangelion. The Gospel before the Gospel before the Gospel. There is a lot packed into those two sentences and its often a let down when I read this to my Catechism kids because its so short and so vague.
If you want to read it literaly, go ahead no one is stopping you from believing that in their original conception snakes had arms and legs. A lot of saints and artists didn't see the serpent as a little grass snake, but as a giant Basalisk sort of creature. Something so fearsome that it would shake someone from a state of grace. In any event there's a lot of good and useful ways to read this literally.
Allegorical, the serpent is Satan, the only important distinction to make is that Satan is not literary the Serpent so you ought to keep the literal inferences to.the literal sense and the allegorical inferences to the allegorical sense.
In the moral sense, this might be the curse that all those who lead others out of a state of grace inflict upon themselves. It is a just punishment for being a deceiver. When you lay object your belly you cannot see the heavens and loosing the beatific vision is precisely what Lucifer earned for himself through his pride.
The anagogical sense is probably the most important sense In which to read this scripture because it carries within it God's promise of a redeemer. But since you didn't ask about that line, the next line, there is no sense rehashing it. But what this might mean for eternity is that Satan will be cursed and derided by creation forever, even though some created beings may find him more attractive than the God Himself.