Csdrhrt

Here is how my home network is set up:

There is an ISP-provided gateway which does DHCP for 192.168.29.0/24. I connected two routers to this gateway as clients, (R1 and R2, with respective IPs 192.168.29.2, 192.168.29.3).

The routers do DHCP under 192.168.0.0/24 and 192.168.1.0/24.

As a client on, say, R2, (192.168.1.3), I would like to reach a client on R1 (the printer, 192.168.0.2). I set up a static route in R2 to let it forward 192.168.0.x requests to 192.168.29.2, which is R1:

However, it appears that R1 doesn't accept the request. I'm guessing it looks like a request from WAN to R1, (which it sort of is), and I have no idea what setting to even look for to let it accept this. And, accept what? What would I be trying to accept -- "packets from outside to inside"? I'm not sure how to even describe this.

Running a traceroute to a R1 client shows that it's hitting R1. Nothing happens then, it's a time-out.

joseph@MBA : ~

[130] % traceroute 192.168.0.5 

traceroute to 192.168.0.5 (192.168.0.5), 64 hops max, 52 byte packets

 1  r2 (192.168.1.1)  4.888 ms  4.537 ms  3.970 ms

 2  192.168.29.2 (192.168.29.2)  5.185 ms  5.291 ms  7.068 ms

Where do I go from here?

The easiest option for you would be to have all your devices in 192.168.29.0/24 subnet. Don't use the WAN port on either R1 or R2, and connect all cables to the LAN ports.

You need to also disable DHCP server on R1 and R2 so that only the GW will provision IP addresses via DHCP.

This way you don't need to consider routing at all.

Original answer:

I assume that you don't have NAT enabled in R1 or R2, which must be the case.

In order for routing to work between two clients in different networks, both ends must have proper routing table entries set:

R2 must have the entry:

Route network 192.168.0.0/24 via 192.168.29.2

R1 must have the entry

Route network 192.168.1.0/24 via 192.168.29.3

You need to have these entries both ways, because IP packets are forwarded in a stateless fashion- Each router looks only at the IP packet destination address and consults the routing entry for that address.

So, if the other router does not have to proper entries, it will forward the reply packets to wrong router, in this case the GW, which is the default route assigned in the router.

You didn't mention the brand and model of the routers so the answer can be just in general...

As you have mentioned in the comment for previous port and didn't mentioned in the original request there is NAT in place what is quite important part of the issue...

R1

route 192.169.1.0/24 via 192.168.29.3

R2

route 192.168.0.0/24 via 192.168.29.2

NAT

In general all the "cross network" traffic will come to the same interface as other (let say internet) traffic so for your last part of the question it will come to the "next" router into outside interface. Physically it will use the Switch device stated on the schema in original post - request. The most probably you will have to allow this traffic to not be blocked.

The firewall/NAT will have to be changed to reflect your expectation...

• you can keep NAT for outgoing traffic without change so all traffic going from 192.169.1.0/24 will be sNATed to 192.168.29.3 (including traffic for destination in 192.168.0.0/24). You will not be able to differentiate between the source devices behind the R2. For allowing incoming traffic you would need to allow source IP 192.168.29.3 @R1.




• you can exclude the traffic with destination 192.168.0.0/24 to be sNATed on R2 so on R1 (and on the devices on 192.168.0.0/24) you will see original source IP for the traffic. For allowing incoming traffic you would need to allow source IP 192.168.1.0/24 @R1 and in case you would like to allow traffic originated on R2 you would allow also source IP 192.168.29.3 @R1.




• other option may be creating tunnel (e.g. ipsec) between R1 and R2 and in that case you can bypass this NAT / firewall "issue" using routing using virtual interface or by using crypto maps (in case of ipsec). In case of this option you can even static routes handle via crypto maps. But here it would be more brand specific to point out "correct" key words to search for more information or providing specific hints.