discrepancy in default routes listing

Question

have machine with two network interfaces: Ethernet and WiFi. Primary connection to internet is via Ethernet and this utilize static IPv4 settings. When connect wifi (utilizing DHCP) to wifi router with another internet connectivity, have (as expected) two default routes with different metric in system. INternet goes via wifi (because of lower metric), this is fine.

When perform wifi disconnect, internet goes back to ethernet and work OK, but when perform command netsh in ip sh ro got two default routes in listing. One is from ethernet adapter metric 256 and second is remaining default route from (now disconnected) wifi adapter with metric 0. This route is unpingable (as expected).

Publish  Type      Met  Prefix                    Idx  Gateway/Interface Name
-------  --------  ---  ------------------------  ---  ------------------------
No       Manual    256  0.0.0.0/0                  22  10.12.70.65
No       Manual    0    0.0.0.0/0                   7  192.168.148.251

When perform netstat -rn got only one default route with metric 281

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0      10.12.70.65      10.12.70.66    281

Why is there this discrepancies between both listings? Its a bug or it have some hidden meaning? (number 281 seems to be substraction of route metric and interface metric)

UPDATE:

command netsh in ip sh config Wifi look also like this

Configuration for interface "WiFi"
    DHCP enabled:                         Yes
    Default Gateway:                      192.168.148.251
    Gateway Metric:                       0
    InterfaceMetric:                      55
    DNS servers configured through DHCP:  192.168.148.251
    Register with which suffix:           Primary only
    WINS servers configured through DHCP: None

command netsh in ip sh addresses WiFI

Configuration for interface "WiFi"
    DHCP enabled:                         Yes
    Default Gateway:                      192.168.148.251
    Gateway Metric:                       0
    InterfaceMetric:                      55

command powershell "Get-NetRoute -DestinationPrefix "0.0.0.0/0" | format-list -property *"

Publish               : No
Protocol              : NetMgmt
Store                 : ActiveStore
AddressFamily         : IPv4
State                 : Alive
ifIndex               : 7
Caption               :
Description           :
ElementName           :
InstanceID            : :8:8:8:9:55A55;C<8;@B8;>B8<?;55;
AdminDistance         :
DestinationAddress    :
IsStatic              :
RouteMetric           : 0
TypeOfRoute           : 3
CompartmentId         : 1
DestinationPrefix     : 0.0.0.0/0
InterfaceAlias        : WiFi
InterfaceIndex        : 7
InterfaceMetric       : 55
NextHop               : 192.168.148.251
PreferredLifetime     : 00:59:59
ValidLifetime         : 00:59:59
PSComputerName        :
CimClass              : ROOT/StandardCimv2:MSFT_NetRoute
CimInstanceProperties : {Caption, Description, ElementName, InstanceID...}
CimSystemProperties   : Microsoft.Management.Infrastructure.CimSystemProperties

Publish               : No
Protocol              : NetMgmt
Store                 : ActiveStore
AddressFamily         : IPv4
State                 : Alive
ifIndex               : 22
Caption               :
Description           :
ElementName           :
InstanceID            : :8:8:8:9:55<<55;:8;<8A:8@?55;
AdminDistance         :
DestinationAddress    :
IsStatic              :
RouteMetric           : 256
TypeOfRoute           : 3
CompartmentId         : 1
DestinationPrefix     : 0.0.0.0/0
InterfaceAlias        : ETH0
InterfaceIndex        : 22
InterfaceMetric       : 25
NextHop               : 10.12.70.65
PreferredLifetime     : 10675199.02:48:05.4775807
ValidLifetime         : 10675199.02:48:05.4775807
PSComputerName        :
CimClass              : ROOT/StandardCimv2:MSFT_NetRoute
CimInstanceProperties : {Caption, Description, ElementName, InstanceID...}
CimSystemProperties   : Microsoft.Management.Infrastructure.CimSystemProperties

UPDATE2:

When unplug wifi adapter from USB slot, than replug it back again, default route related to this adapter disappear from all lists.

Answer 1

You are seeing here the behavior of the driver for the WiFi router. When not connected, it sets the metric to zero, as long as the device is powered on.

I have searched the meaning of a zero metric, and it seems to depend on the manufacturer. For example, for some Cisco devices it means a direct cable connection (so zero overhead). For other devices, this only means an invalid parameter.

Perhaps the reference that conforms the most to your experience, I found strangely enough in the Contiki Operating System:

/* These specifiy the sink's routing metric (0) and the maximum
   routing metric. If a node has routing metric zero, it is the
   sink.

The word "sink" seems to mean the edge of the network, meaning that there is nothing to be connected further on.

Apparently, the driver to your device sets the metric to zero to signal that the device exists, but there is no further connection possible beyond it. Windows seems to understand it in a similar way.