Here is the sentence:
There are ways around requiring Proxy ARP on a NAT device, but that involves using a Static Route on the Router to manually instruct it to send packets which must be translated to the Firewall’s interface. While effective, this solution does not scale.
Here is a similar sentence that won't require understanding the technical jargon:
There are ways to get around requiring toilet paper, but that would involve getting your hands dirty. While effective, this solution does not scale.
The idea is the "other solution" works, is feasible and would technically accomplish the goal. BUT, is not ideal or even suggested as a "good solution" to the problem.
The word "effective" works, but I feel it conveys too much positive sentiment for what I am trying to accomplish.
"Feasible" is also a potential candidate, but leaves to vague about the solution working at all (aka, it's possible, doesn't mean 100% certain to work). The solution in both of the sentences above absolutely work, but are absolutely not the most ideal way of doing things, and therefore not effective solutions to the problem.
Single word preferred, but willing to do multi-word. Would rather avoid a colloquialism.