Re: internal network

[Samuel Sieb]

On 3/1/25 4:18 PM, Will McDonald wrote:
> On Sat, 1 Mar 2025 at 22:22, Patrick Dupre via users 
> <[e-mail] > 
> wrote:
> I am lost.
>
> I had a configuration with was working, but my usb WiFi doogle does
> not work anymore.
> The configuration which was working
>
> Doogle on PC A with 2 ethernet cards.
> One connected to PC B: a laptop
> one connected to PC C
>
> Now, The laptop PC B is connect to a wifi mobile.
> It works
> wlp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>          inet 192.168.43.115  netmask 255.255.255.0  broadcast
> 192.168.43.255
>
> I set the ethernet interface "shared to other computers"
> enp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>          inet 10.42.0.1  netmask 255.255.255.0  broadcast 10.42.0.255
>
> Now I am trying to connect this ethernet card to PC A
>  >From the network interface, It tried
> "shared to other computers"
> and
> "Automatic (DHCP)",
> but none of them allow me to make the connection
> (connecting for ever).
> Hence, I tried manually
> 10.42.0.5  255.255.255.0
> It connected
> enp1s0 flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>          inet 10.42.0.5 netmask 255.255.255.0  broadcast 10.42.0.255
>
> But the 2 computers do not talk together
>  >From PC B to PC A:
>   ping 10.42.0.5
> PING 10.42.0.5 (10.42.0.5) 56(84) bytes of data.
>  >From 10.42.0.1 icmp_seq=1 Destination Host Unreachable
> traceroute to 10.42.0.5 (10.42.0.5), 30 hops max, 60 byte packets
>   1  Sappho (10.42.0.1)  3068.823 ms !H  3068.691 ms !H  3068.614 ms !H
> route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref   
> Use Iface
> 0.0.0.0         192.168.43.1    0.0.0.0         UG    600    0     
>    0 wlp2s0
> 10.42.0.0       0.0.0.0         255.255.255.0   U     100    0     
>    0 enp3s0
> 192.168.43.0    0.0.0.0         255.255.255.0   U     600    0     
>    0 wlp2s0
>
>  >From PC A to PC B:
> same behavior
> route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref   
> Use Iface
> 10.42.0.0       0.0.0.0         255.255.255.0   U     100    0     
>    0 enpls0
> 192.168.122.0   0.0.0.0         255.255.255.0   U     600    0     
>    0 virbr0
>
>
> I think if I'm reading your description correctly, this is roughly your 
> topology and addressing?
>
> https://photos.app.goo.gl/sWCqtQNNBBzBuGWk9 <https://photos.app.goo.gl/ 
> sWCqtQNNBBzBuGWk9>
>
> If my understanding is correct
> the default gateway (0.0.0.0) from PC A (10.42.0.5) needs to be PC B
>
> (10.42.0.1)

Yes, DHCP should be working which would set the gateway, but he manually 
configured it and probably didn't put the gateway.  Even without the 
gateway, the ping should have worked.
> you probably don't want 192.168.0.122.0 to be a gateway configured on PC A

That's not a gateway.  That's the VM bridge interface with no gateway.
> you probably need ip_forwarding (net.ipv4.ip_forward) enabled on PC B
>
> if it's being used as an ersatz router

That should have already been set by using the sharing option.