It is very unsafe to walk with a broken ankle. This is because the tissues in the ankle have not recovered yet. Because of this, it is still not in the best condition for walking. Nonetheless, broken ankle recovery should be aided by some physical therapy which would include some walking exercise. These would be very slow-paced and easy as opposed to walking as though the foot is fine.
Another important thing to note with the broken ankle recovery in terms of being able to walk would be that it is possible to wear specialized footgear that will immobilize and cushion the joints but will still allow walking. Typically, it would take about a week of pure rest and recovery before it would be advisable to practice walking with the broken ankle.