We have a 3750EI that has a L3 WAN port and a L3 LAN port. Let's say the WAN port is 126.96.36.199 and is plugged into gi1/0/1. The external interface of our ASA is 188.8.131.52 and is plugged into gi1/0/2. The internal interface of the ASA is 172.16.120.10 and is on vlan 90. The issue I'm running into is I'm exhausting my default gateway right off the bat. My clients will connect to the data vlan and I have the 3750's default gateway to the internal interface of the ASA. I am unsure of what to do now as I don't know what to route to the external interface of the ASA.
Thank you in advance for any assistance
The default gateway for users will be the inside interface of the firewall (172.16.120.10). The default route on the firewall will point to the LAN interface of the 3750. The 3750 has a default route to the internet via it's WAN port - you don't have to route anything back inside since user traffic gets NAT'd to the external interface of the firewall and the 3750 already knows about this since it's directly connected.