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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 default-gateway or default-network commands.

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.

You also say that the 10.6.9.10 address that you want to use for the gateway is another switch. You need to make sure that address really is a gateway for that network. Do not confuse the layer-2 LAN with the layer-3 routing. The address you use as a gateway needs to be a router (or layer-3 switch) that knows how to get to other networks.

You should edit your question to include a good description (a diagram would be great) of how your network is connected, and the full switch configurations. That would help us give you a more specific answer.