A client's network has a PIX 515 and an ASA5505 on the internal network. DHCP sets the PIX as the default-gateway for all of the network hosts, bar four. These four machines are configured to use the ASA as their default-gateway - this is a solution for a convoluted setup involving VPNs and static NATing to other private IP addresses...
In short, these four machines are unable to route all non-VPN traffic through the PIX, despite the ASA having the PIX as it's 'gateway of last resort'. Every packet is dropped by the implicit deny rule on the inside interface.
How can I get the packets to passed to the PIX successfully?
Config of the ASA is attached.
I think this is because your default gateway is pointing back out the inside interface and you don't have a translation set up for that.
I would try adding the intra-interface command with the following NAT exemption:
access-list nat0 permit ip Net_LAN 255.255.255.0 any
nat (inside) 0 access-list nat0