I have a Balance One with 5 WAN package. It has 3 identical package on the first 3 WANs.
Recently I added another package for use on the 4th WAN and setup an internal VLAN to use only this WAN with an outbound policy enforced WAN 4 only.
When testing I found that some users directed to the first 3 WANs were being directed to the 4th WAN.
Is there a way or stopping this from happening?
Sure. By default all traffic will be load balanced across all WANs.
You need two outbound policies. One that says load balance across WAN1-3 for any source IP. Another policy above that that identifies the source IP/subnet of the new VLAN and is set to Priority with WAN4 at the top.
Will the load balance policy setup to use WAN 1-3 allow users of that policy to access the WAN 4 ever?
No. Not until you are using firmware 8 and can then choose to failover to an additional rule if WAN1-3 are all down (ie a priority rule that says use WAN1-4 in that priority).