I am new to Cisco in general and have the following setup:
GigabitEthernet0/0 contains an IP address that is connected to our provider/BGP drop; GigabitEthernet0/1 contains various IP addresses assigned ending in .1 for the IP prefixes we announce to the Internet; this is also the Interface that all of our devices are plugged into via our switch <--> GigabitEthernet0/1 connection.
We want our primary IP address on GE0/0 to be on our primary assigned IP network, such as a.b.c.252 while keeping .1 on GE0/1 for a gateway for our local machines/equipment. Currently when traceroutes or the like come into the network, they get responded to with the IP assigned from our uplink to GE0/0. We'd like this instead to be an IP from our own assigned prefix for identification/notification/consistency sake. (We'll keep the IP from our uplink as a secondary IP).
When I try to assign .252 to GE0/0 and .1 to GE0/1, I get the usual errors about the subnet already existing on another interface.
How do I go about doing this? How do I assign IP in A.B.C, such as A.B.C.252 to GE0/0 as the primary IP address while assigning A.B.C.1 to GE0/1 so that clients on the network can use it as a gateway?
Or, is there a way to allow those on the LAN to use IPs on GE0/0 even though they're plugged into GE0/1, without borking anything too bad? And more to this point even more so, and going a bit off the rails but curious to know if it's possible - if we have three distinct prefixes assigned from RIPE, and wanted to have traceroutes and what-have-you respond with the .1 IP from the beginning of each subnet to the requestor, would this be possible? I am imagining something to do with NAT and matching response with a given source IP for certain ICMP packets (but this wouldn't work for, say, UDP traceroute?). Any ideas there either?
Thanks in advance!