The subnetworks work fine within themselves and pings reach their destinations but pings can't go through the router and reach the other LAN. I can ping the interface of the router that is on the same side of the origin of the ping but not the other one. It's as if the router is acting like a wall of brick. As far as I can tell the configuration of the interfaces are fine and the IPs of the hosts are as well considering I can ping them within their own subnetworks. The switches seem to work as intended within their own network. I'm fairly new at networks and I've searched online without finding any fix that worked for me. At one point I was considering a default gateway problem but even if it is I don't know what I would have to do to fix it. IP addresses with their default gateways of all the elements I've also looked at the Router0 "show ip route" but can't notice anything that could help me.
1 Answers
Hello Nathan Cournoyer,
It looks like the problem resides with your default gateway settings.
Let me go through the ip routing process for you (sort of).
Let's say PC1 wants to send an ICMP ping to PC3 in the other network (LAN2). So you type in PC1 terminal ping 192.168.2.145. PC1 is first going to determine whether routing is necessary by checking whether PC3 is on the link. According to PC1's IP address and subnet mask, PC1 determines that only hosts 192.168.1.1-254 (192.168.1.0/24) are on the link, therefore 192.168.2.145 is not on the link and routing is necessary. As a result, PC1 sends the ping packet to its default gateway for routing. You currently have 192.168.1.0 as your PC1 default gateway, which is incorrect in two ways. 1) PC1 cannot reach the router through this address because the Router0's interface on LAN1 is 192.168.1.127. 2) 192.168.1.0 is typically used as a subnet ID. I don't think it can be used to routing.
To solve your problem, you need to set the default gateway of both LANs' hosts to the router interface's IP on the same respective LAN.
I think the previous sentence is confusing. Let me detail your setup
| Device | Interface | CIDR | Default Gateway |
|---|---|---|---|
| Router0 | G0/0 | 192.168.1.127/24 | |
| G0/1 | 192.168.2.159/24 | ||
| PC1 | NIC | 192.168.1.97/24 | 192.168.1.127 |
| PC2 | NIC | 192.168.1.98/24 | 192.168.1.127 |
| PC3 | NIC | 192.168.2.145/24 | 192.168.2.159 |
| TFTP Server | NIC | 192.168.2.146/24 | 192.168.2.159 |
For IPv6, it should be largely the same logic as IPv4. I don't think you need to setup IP addresses for the switches, unless they need that for internal web servers and others. You can technically replace the router with a layer 3 switch. You may not need a full-blown router for inter-LAN routing.
I learn computer networking on my own, so my knowledge may be incomplete and/or incorrect. Please point out any problems.
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