Can someone help me? I have two subnets, 192.168.100.0 and 192.168.1.0. they are connected to each other via two “gateways"


Easy enough. Two gateways because both networks were originally separate and are now joined. What I want to do is to be able to associate a specific ip address on the 192.168.1.0 side with a specific ip address on the 192.168.100.0 side. So any requests to 192.168.1.6 will go specificity to 192.168.100.6 and any requests for 192.168.1.5 will go to 192.168.100.5, ect... I do not want port forwarding. For the sake of conversation i might want two webservers running on the 192.168.100.0 side both running port 80. or ping 192.168.1.5 to see if 192.168.100.5 is up. I want all requests for a specific ip on the 192.168.1.0 side to be sent to the 192.168.100.0 side to a specific ip address. I have many free 192.168.1.0 ip address. I can not combine the two networks in to one, the IP address have to stay their ip addresses. Also I don’t have access to the 192.168.1.1 Gateway, can't change it, can't log on to it, can even look at it. But I can do what ever to the 192.168.100.1 gateway. On it now I am running redhat 7.3 using iptables and NAT. Is there something called static NAT or something that can accomplish this? Plus how do i get the 192.168.100.1 gateway's eth0 to actually not ignore stuff headed for 192.168.1.0??? Do I have to do ifconfig eth0:1 blah blah.... Any help would be appreciated. From what I have been reading this can be accomplished with some IPTABLES rules but I am not sure even where I begin.
Thanks

Although old, this is still an interesting question; can you supply more information?

Do you indeed want to map all IP addresses on Net-1 (192.168.1.0) to the corresponding IP address on Net-2 (192.168.100.0)? 192.168.1.n ==> 192.168.100.n

The topology isn't clear -- Does this mean that each gateway has an additional NIC connected by a cross-over cable to the other?

Although we might be curious as to why you can't access the Net-1 Gateway (192.168.1.1), we don't need that info. to solve the problem.

The important question is whether your Net-2 gateway (192.168.100.1) "sees" all traffic on Net-1. If the packets on Net-1 never get to a router under your control, you can't forward them to anything on Net-2.

Do the IP addresses on Net-1 (192.168.1.n) represent real machines; and, if so, do you want to
a) divert or
b) duplicate
the packets on Net-1 to Net-2?

Yes, there is something called static NAT (SNAT), & it may be what you need.

Where to begin w/ IPTABLES rules is a huge Q; "RTFM", while always a good idea, will only scratch the surface.