Re: Routed network can't reach outside network

On 7/23/20 6:14 PM, Rui Correia wrote: Back in your original message, you said this: On 7/19/20 6:54 AM, Rui Correia wrote: But in a later message you say this: On 7/23/20 10:34 AM, Rui Correia wrote: So which is correct? It will probably make no difference (unless traffic leaving your "KVM Host" isn't actually using the interface named "wlo1", and in that case it makes *all* the difference!), but I would change this to simply: <forward mode='route'/> The purpose of the "forward dev" is commonly misunderstood as having something to do with routine, but it doesn't - it only serves to add an iptables rule that will block traffic if it's coming from or going to any interface other than (in this case) "wlo1". ie. it's a security knob, not a routing knob; if you're not concerned about rogue guests then at best it's just creating extra overhead for each packet, and at worst it could be blocking traffic if it's misconfigured. As for checking with wireshark/tcpdump, mainly the intent is just to see, when you send a packet from one end or the other, whether a corresponding packet shows up in the output of wireshark/tcpdump. As an example, let's say that you are trying to ping (from your original diagram) "desktop manjaro" (10.0.0.11) from "debian 10 VM" (10.2.2.10). First start a ping in a shell on debian 10 VM", then run a command like (as root) this on the KVM Host: tcpdump -i virbr2 -n host 10.2.2.10 You should at least see one icmp "echo request" packet for each ping that is sent. You might even see an icmp response (and if so, hopefully is is an icmp echo reply, rather than destination unreachable or something like that). If you see the outbound icmp echo request and an echo reply, then the problem is on your host or in the guest. If you see an echo request but no echo reply, then look at the next step out - wlo1 interface on the KVM host: tcpdump -i wlo1 -n host 10.2.2.10 You should still see the outbound echo request. If not, then again your problem is on the KVM host. If you see the echo request, but no reply, then you need to go look on "manjaro desktop". Run the same tcpdump command there (as root), but replace "wlo1" with whatever is the name of the ethernet device on that host connecting it to the network. At this point you may see an echo request *and* an outgoing echo response, but not see that response back at the KVM host. That's when you'll want to rerun tcpdump telling it to display the MAC address of the packets: tcpdump -i <whatever-interface-name> -e -n host 10.2.2.10 Now you can look at the MAC address in the tcpdump output - it should contain the MAC of the KVM host, *not* the MAC of your router. If it has the MAC of your router, then you haven't added a routing table entry to the manjaro desktop's network config. Do that. (or, possibly you just want to add a route to the router. That will work, but will result it a lot of duplicated traffic and ICMP redirect packets from the router to the manjaro desktop). Anyway, there are many paths this can take, but that gives you an idea of how to use tcpdump. (you could do the same thing with wireshark, it's just a lot more overhead and lots of info when you really need very little (and also requires that wireshark be installed and a desktop session open, on all the machines involved).