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Sorry! Disregard my previous post. I re-read your original post. The mask to denote 64.68.96.0 to 64.68.127.255 the mask is 255.255.224.0. If you did need the inverse mask it would be 0.0.31.255.
64.68.127.255 is not a subnet mask. I suspect that you mean that the subnet mask is 255.255.128.0. However, when you enter it into the PIX, I suspect that you need to use the inverse mask which would be 0.0.127.255.
