As YLearn points out, you need to determine if the switch is operating as strictly a layer-2 switch, or is it actually routing (layer-3). If it is routing, then you do not want to use the
You should not use the
ip default-gateway commands on a router that is acting as a router, and the
ip default-network command is really for IGRP, which doesn't understand the default route; you can use a static default route.
Cisco has a document that explains the differences: Configuring a Gateway of Last Resort Using IP Commands.