How do I observer the default-gateway set on a switch? I am not able to view it with the "show running-config" command.
Use the command "show ip default " , this will list the gateway on all layer 2 switches and any layer 3 switch that has routing turned off .
You should fing "ip default-gateway" in the config.
you can also have a IP route 0.0.0.0 0.0.0.0 entry if ip routing is enable.
The last possibility, (if the switch is working and no default gateway configure), is that the router is doing proxy-arp. This is a security issue but still possible.
show running-config should list it.Check weather it is configured in the switch.
Btw what kind of this switch is.