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Current Network Map

Network layout

My noob question is why any device on network 192.168.10.0/24 can ping any device on network 192.168.1.0/24 and the opposite doesn't work?

I need to be able to connect to my Server(192.168.10.100) from Computer A(192.168.1.144) but route is unreachable.

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The fact that devices on network 192.168.10.0/24 can (without configuring a static route on those devices) ping devices on network 192.168.1.0/24 implies that router EdgeRouter-X is actually not acting simply as a router but doing Source NAT, translating the address range 192.168.10.0/24 to its uplink address 192.168.1.135. So addresses in the range 192.168.10.0/24 are invisible beyond that router.

You have three possible solutions:

  1. The classical solution: get rid of NAT on EdgeRouter-X and configure proper routing. Since the network 192.168.1.0/24 is not a single exit network this implies configuring a static route for network 192.168.10.0/24 via 192.168.1.135 on all the hosts in network 192.168.1.0/24, including the ISP modem/router, except of course EdgeRouter-X itself which has a connected route for that network.

  2. Extra hop routing: again, get rid of NAT on EdgeRouter-X, but configure the static route for network 192.168.10.0/24 via 192.168.1.135 only on the ISP modem/router. This means that all traffic from hosts in 192.168.1.0/24 goes to the ISP modem/router which then forwards it to EdgeRouter-X even though the host could have sent it there directly. (The so-called extra hop.) The ISP modem/router will typically try to tell the host to send future traffic directly to EdgeRouter-X by way of an ICMP Redirect message, which the host will typically ignore because ICMP Redirect is considered a security risk.

  3. Heaping workaround on workaround: configure port forwarding for Server 192.168.10.100 on EdgeRouter-X, making it reachable on the address 192.168.1.135. I won't go into detail on this because it is really too kludgy.

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    Thank you for your answer. I had already set everything as described in solution 2 and still no luck but for anyone searching I really just getting my feet wet in networking and I didn't check my firewall rules before searching and the issue was there. ER-X on basic setup wizard it drops any WAN_IN connection by default. I added a rule to accept if source IP was in 192.168.1.0/24 network. Thank you again.
    – Χρήστος Καρανίκας
    May 12, 2022 at 9:26

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