A lot of enterprise ageements/awards contain a re-employment limitation - 6 or 12 months is usual following redundancy.
Apart from the above, you can be re-employed at any time, but the taxation benefits of redundancy will disappear if the ATO deems the redundancy was not genuine.
ATO tax ruling 2009/2 does not have a specific time - see paras 306 to 309.
Suggest you get a private ruling from the Tax Office - they are not that hard to do, or get your accountant to do it. Then weigh up whether any loss of tax benefits is offset by future employment.