|Which is correct?
There are a number of methods you can use to capture VoIP calls ___ a LAN.
b. off of
Although “off of” is widely considered ungrammatical, it’s sometimes the better choice — and I think this is one case where “off of” lends greater clarity to the sentence. The sentence is correct either way but to my mind, “off of” is a better choice.
Many grammar experts maintain that “off of” is always wrong but I think that is a rule that is made to be broken, at least occasionally.
The most common arguments against “off of” are that “of” is unnecessary and that two prepositions should never be placed side-by-side.
On Motivated Grammar, Gabe Doyle counters those arguments:
And yes, you can put two prepositions next to each other, as in this unobjectionable example:
(2) I pulled a coat out of the closet.
Going on to a somewhat more complex objection, antonymic phrases do not have to share structures or prepositions. The fact that you get on and not on of a train doesn’t mean that you have to get off and not off of it. Consider:
(3a) I put the sandwiches into the picnic basket, but someone has pulled them out of it.
(3b) One velociraptor was in front of Muldoon, the other next to him.
The point about “out of” is an interesting one because you hear “of” left out of that sentence increasingly, as in “I pulled my coat out the closet.” Maybe the false rule about double prepositions will evolve through use but it’s not there yet. In the meantime, let’s consider each case and select the best choice for the sentence in question.