If multiple interfaces have ip addresses from the same subnet and the default GW is also on the same subnet range, which interface will be used.
The ProxySG always picks the lowest interface ID for default route.
The only way to force the ProxySG to use a different interface than the current interface for default route is to disable the current interface.
ProxySG will select the next lowest ID interface for default route.
In our example, after interface 1:0 is disabled, routing table will be updated and changed to Netif=2:0 for default route.
Once the routing table is changed, enabling interface 1:0 does not make routing table revert back.
However, whenever the ProxySG reboots, interface 1:0 will be selected for default again.