Without knowing more about the configuration of the router and about the history and environment we can not tell why the Ethernet is the router id instead of the loopback. There are several reasons why the Ethernet may be the router ID instead of the loopback:
- perhaps the loopback did not exist or was shut down when the OSPF process started. In this case it would choose the Ethernet.
- perhaps the OSPF process is configured to use the Ethernet instead of the loopback.
- perhaps there is more than 1 OSPF process on the router. Each OSPF process must have a unique router ID. If one process chose the loopback as router ID then the other process must choose some other interface and may have chosen the Ethernet.
As long as the router ID is unique I do not believe that there is much reason for you to be concerned which interface it is.
I would not think that there would be any relationship between the loopback being used for IPSec tunnel peering and the OSPF router ID, but perhaps someone thought there was (or should be) a relationship and configured it that way.
If there have been configuration changes (changing IP addresses on interfaces, adding or removing loopback interfaces, adding or removing subinterfaces) when you power cycle the router it is possible that the OSPF router ID may change. It should not be a big deal whether it changes or not.
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