Timeout for access from Guest VM to Host

Question

I use virt-manager to administer my virtual machines. I would like to communicate a virtual machine (Windows) with the host machine (GNU/Linux).

I use the default network interface, which is a bridge in NAT mode, with the network address 192.168.122.0/24. When I listen on the host 192.168.122.1 on port 12345, I check with my guest machine with netcat :

nc -vz 192.168.122.1 12345

I get the following answer :

Warning: forward host lookup failed for hostname: h_errno 1101: HOST_NOT_FOUND
hostname [192.168.122.1] 12345 (?): TIMEOUT

And I get the same answer on any interface.

But if I do the same on the external network gateway 192.168.0.1, I get :

gateway.lan [192.168.0.1] 12345 (?) open

How can I fix it ?

Answer 1

I use the default network interface, which is a bridge in NAT mode, with the network address 192.168.122.0/24. When I listen on the host 192.168.122.1 on port 12345, ... I get Warning: forward host lookup failed for hostname:

First: try in Bridged Mode to get everything on one subnet. That usually works fine.

Second: If you wish to revert to NAT, try IP addressing for communication between host and guest. I do this. Name addressing is more complicated.

I do prefer Bridged for this.

Answer 2

Under Red Hat distributions the default firewall used is firewall-cmd. To be able to access from the guest machine to the host machine simply open the specific port via the firewall :

sudo firewall-cmd --zone=libvirt --add-port=12345/tcp

Where libvirt is the area network for virtual machines using libvirt library (virt-manager or cockpit by example).

I did not check but i imagine that under debian distributions for example, just edit the nftables firewall.