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RV042 Smart Link Backup sticks on backup WAN

I have a number of RV042s that are set up as inter-site router (in Router mode) using WAN1. WAN1 connects to an inter-site fiber link, so it's a bit like a site-to-site VPN without the VPN.  And, this path provides the preferred internet connection vai the remote site.

Smart Link Backup is the selected dual WAN mode with WAN1 Primary.

WAN2 connects to a local firewall and to the internet via an ADSL modem - which is lower speed than the WAN1 internet service.

WAN1 pings an IP address at the remote site LAN in order to confirm that the intersite link is up.

WAN2 pings an internet address to confirm that the local internet link is up.

What this should mean is this as I understand it:

As long as the inter-site link is up, WAN1 will remain connected.

This is what we want so that interoffice interconnect can remain even if the remote site internet connection goes down.

So, it should only switch to WAN2 if the inter-site link goes down OR if we pull the intersite cable in order to get internet access through WAN2 (giving up on inter-site connectivity).

Also, as I understand it:

If the inter-site link on WAN1 goes down then the RV042 will switch to WAN2.  This clearly works.

And, when the link on WAN1 returns, the RV042 will switch back to WAN1.

Yet, I am finding these devices "stuck" on WAN2.  I suppose there had been an intermittent failure of the inter-site link that caused this to happen in the first place.  But, they stay there.  They don't switch back to WAN1.

To fix this, I have to manually switch the primary to WAN2 / Save / switch the primary back to WAN1 / Save and then all is back to normal.

This happens every week or two.  It's not hard to fix but it compromises the expected network topology.

Now that I think about it, it appears that the WAN1 connection remains while WAN2 is "on".  Yet, internet routing goes through WAN2 as determined with a traceroute.  That is, I've had no complaints about the inter-site connections going away - even though that's what I'd expect if the backup link had been selected.

The WAN1 IP address in the summary *always* shows pointing to remote on the fiber link.  Well, unless WAN2 is Primary.  Then it shows 

When things are "normal", the WAN2 IP address in the Summary shows

When things are not "normal", the WAN2 IP address shows which points to the local firewall at

When WAN2 shows an address, it's likely that the traceroute to an internet address will go through WAN2.