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Using virt-manager, KVM on Ubuntu, I created a VM with default network configuration (NAT) as described here: https://wiki.libvirt.org/page/VirtualNetworking under NAT mode.

which should have internet connectivity by default. But I am unable to ping internet addresses from the VM. instead, I am getting destination port unreachable from the corresponding host interface

ping results

I am suspecting it is something to do with iptables 'reject-with icmp-port unreachable' configurations in the forwarding table below. The rules were atomatically created by virt manager, but even when I remove the rules, I still get the same problem. any ideas please

Chain FORWARD (policy ACCEPT)
num  target     prot opt source               destination         
1    ACCEPT     all  --  anywhere             192.168.150.0/24     ctstate RELATED,ESTABLISHED
2    ACCEPT     all  --  192.168.150.0/24     anywhere            
3    ACCEPT     all  --  anywhere             anywhere            
4    REJECT     all  --  anywhere             anywhere             reject-with icmp-port-unreachable
5    REJECT     all  --  anywhere             anywhere             reject-with icmp-port-unreachable
6    ACCEPT     all  --  anywhere             192.168.100.0/24     ctstate RELATED,ESTABLISHED
7    ACCEPT     all  --  192.168.100.0/24     anywhere            
8    ACCEPT     all  --  anywhere             anywhere            
9    REJECT     all  --  anywhere             anywhere             reject-with icmp-port-unreachable
10   REJECT     all  --  anywhere             anywhere             reject-with icmp-port-unreachable
11   ACCEPT     all  --  anywhere             anywhere            
12   ACCEPT     all  --  anywhere             anywhere            
13   ACCEPT     all  --  anywhere             anywhere            
14   DOCKER-USER  all  --  anywhere             anywhere            
15   DOCKER-ISOLATION-STAGE-1  all  --  anywhere             anywhere            
16   ACCEPT     all  --  anywhere             anywhere             ctstate RELATED,ESTABLISHED
17   DOCKER     all  --  anywhere             anywhere            
18   ACCEPT     all  --  anywhere             anywhere            
19   ACCEPT     all  --  anywhere             anywhere            

and NAT rules

Chain POSTROUTING (policy ACCEPT)
num  target     prot opt source               destination         
1    RETURN     all  --  192.168.150.0/24     base-address.mcast.net/24 
2    RETURN     all  --  192.168.150.0/24     255.255.255.255     
3    MASQUERADE  tcp  --  192.168.150.0/24    !192.168.150.0/24     masq ports: 1024-65535
4    MASQUERADE  udp  --  192.168.150.0/24    !192.168.150.0/24     masq ports: 1024-65535
5    MASQUERADE  all  --  192.168.150.0/24    !192.168.150.0/24    
6    RETURN     all  --  192.168.100.0/24     base-address.mcast.net/24 
7    RETURN     all  --  192.168.100.0/24     255.255.255.255     
8    MASQUERADE  tcp  --  192.168.100.0/24    !192.168.100.0/24     masq ports: 1024-65535
9    MASQUERADE  udp  --  192.168.100.0/24    !192.168.100.0/24     masq ports: 1024-65535
10   MASQUERADE  all  --  192.168.100.0/24    !192.168.100.0/24    
11   MASQUERADE  all  --  172.17.0.0/16        anywhere            
12   MASQUERADE  all  --  192.168.122.0/24     anywhere            
13   MASQUERADE  all  --  192.168.223.0/24     anywhere            

Thanks,

2
  • The default stuff doesn't create a VM which is on your LAN. You need to create a bridge network interface in your host and then get your VM to use it instead of the default stuff. I do not use netplan, and so only know how to do this the "old" way. See here and here. – Doug Smythies Feb 8 '20 at 16:45
  • The default iptables listings are actually incomplete, not including network interface information. To determine the actual differences between some your REJECT rules we would need to see the outputs for sudo iptables -v -x -n -L and sudo iptables -t nat -v -x -n -L. – Doug Smythies Feb 8 '20 at 16:54

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