Configuring Cisco with several public IP's for NAT on one interface
Posted on 2006-06-15
I have a Cisco 2800 with two Eth interfaces (fe0/0 and fe0/1), one (fe0/0) connected to my LAN and the other one (fe0/1) connected to my "Internet" segment; this Internet segment is in turn connected to 3 ISP routers (one ADSL, one LS, and one VSAT -- let's call them A, B and C). Currently, my Cisco 2800 Internet eth interface (fe0/1) is assigned a public IP from connection A, and default ip outbound routing is directed towards A's router. And I have also defined some NAT's between some other public IP's bought from A and some of my private IP's (on the fe0/0) side. This works fine -- ie, I can establish connections out to the Internet from the LAN, and clients from the Internet can connect to my NAT'ed LAN servers. Basic stuff. Great.
Now, I'd like to use connections B and C. So I have similarly defined some more NAT's, using public ip addresses bought from ISP's B and C, and NAT'ed them to some LAN ip's. And these NAT's don't work (neither TCP nor UDP). Should I do something about the "return path"? ie, I've got only one default route out, towards A's gateway. How should I explain the router that connections/packets first coming onto B/C public IP's should be routed back to B/C's gateways? I can't even get these NAT's to work with B and C public ip's when I hook up a single PC on my "Internet" segment with a public address from B and C.