Outbound Policy Priority: difference between Priority and Overflow?

I have a Balance One and two WANs (let’s call them WAN1 and WAN2). I basically want all traffic to use WAN2 first, but if WAN2 is getting congested to go ahead and use WAN1 as well.

I think my choice is either between Priority or Overflow:

**Priority: ** Traffic will be routed through the healthy WAN connection that has the highest priority.
Overflow: Traffic will be routed through the healthy WAN connection that has the highest priority and is not in full load. When this connection gets saturated, new sessions will be routed to the next healthy WAN connection that is not in full load.
It sounds like under Priority, once WAN2 gets saturated, WAN1 would remain un-used. But under Overflow, WAN1 would be used after WAN2 is full.

Do I have that right? If so, it sounds like I want Overflow.

In my case overflow wrk better because the wan1 has more bandwidth that wan2 but only testing you will find th correct choice

Please find here for better understanding.

Hope this help.

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Thanks for the info.

Load balancing is interesting and has some “gotchas”.

For example, I recently did this test:

  • WAN1: 20mbps upload
  • WAN2: 5mbps upload
  • Task: send 10 SFTP files, in two groups of 5.
  • Algorithm: Overflow, set to prefer WAN1 then WAN2.

What happens is that you start the first batch and it goes out over WAN1. Great.

But then you start sending batch 2 and it goes out over WAN2. (this makes sense, as WAN1 is saturated).

However, at some point WAN1 finishes and is empty, and WAN2 (because it is 1/4 the speed of WAN1) keeps going and going and going.

With perfect knowledge, it would have been faster overall to just upload everything on WAN1 - but of course the Peplink can’t know that, as it doesn’t know in advance the size of an FTP upload.

I’m not complaining about the algorithms: just pointing out that load balancing is complicated and in some scenarios can behave in ways that you don’t expect.

We are doing session load balancing. Hence, sessions in WAN2 will not fallback to WAN1 when the session yet to expire. When the WAN1 is healthy (not saturated), new session will resume in WAN1. This is the expected behavior.

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