No Route To Host from one VM on LAN

Question

I'm quite stumped/frusterated as I can't get postfix to work on one of my VM's. It is a "template" VM and I have setup other VM's with this template fine. The only difference I can really think of is this VM's purpose which is ZoneMinder security software.

I tried using telnet mail.domain.com 25 & ssh [email protected] and I get No Route To Host for both. Both of these work from other VM's inside the LAN and the mail.domain.com is also inside the LAN.

Here is the network config from the VM in question (which is Ubuntu 18 BTW):

root@sub:~# cat /etc/network/interfaces                                                                                                                                                                                                                        
# ifupdown has been replaced by netplan(5) on this system.  See                                                                                                                                                                                                       
# /etc/netplan for current configuration.                                                                                                                                                                                                                             
# To re-enable ifupdown on this system, you can run:                                                                                                                                                                                                                  
#    sudo apt install ifupdown                                                                                                                                                                                                                                        


# The loopback network interface                                                                                                                                                                                                                                      
auto lo                                                                                                                                                                                                                                                               
iface lo inet loopback                                                                                                                                                                                                                                                

# The primary network interface                                                                                                                                                                                                                                       
auto ens3                                                                                                                                                                                                                                                             
#iface ens3 inet dhcp                                                                                                                                                                                                                                                 
iface ens3 inet static                                                                                                                                                                                                                                                
address 192.168.1.255                                                                                                                                                                                                                                                 
netmask 255.255.255.0                                                                                                                                                                                                                                                 
gateway 192.168.1.1                                                                                                                                                                                                                                                   
dns-nameservers 192.168.1.1                                                                                                                                                                                                                                           
dns-search domain.com

Here is the Hosts file:

root@sub:~# cat /etc/hosts                                                                                                                                                                                                                                     
127.0.0.1       localhost sub.domain.com    sub                                                                                                                                                                                            
::1             localhost6 sub6.domain6.com sub6                                                                                                                                                                                           

# The following lines are desirable for IPv6 capable hosts                                                                                                                                                                                                            
::1     localhost ip6-localhost ip6-loopback                                                                                                                                                                                                                          
fe00::0 ip6-localnet                                                                                                                                                                                                                                                  
ff02::1 ip6-allnodes                                                                                                                                                                                                                                                  
ff02::2 ip6-allrouters                                                                                                                                                                                                                                                
ff02::3 ip6-allhosts

And finally, I was able to SSH to other VM's in the LAN so I'm quite stumped. Any pointers or more information needed let me know.

Thank You

Update:

I am able to ping mail.domain.com from other VMs but not the one in question, I have never had this issue before.

Eg:

root@sub:~# ping mail.domain.com                                                                                                                                                                                                                  
PING mail.domain.com (192.168.1.237) 56(84) bytes of data.                                                                                                                                                                                               
From 192.168.1.255 (192.168.1.255) icmp_seq=1 Destination Host Unreachable                                                                                                                                                                                            
From 192.168.1.255 (192.168.1.255) icmp_seq=2 Destination Host Unreachable                                                                                                                                                                                            
From 192.168.1.255 (192.168.1.255) icmp_seq=3 Destination Host Unreachable

Update2:

I have now removed the NIC from the VM and added a new one in case there was duplicate MAC issue.

I changed the IP address and the DNS entry in the gateway.

I rebooted the gateway after the above two steps still didn't work and I have been flushing the arp cache via ip -s -s neigh flush all periodically along w/ reboots just to make sure that isn't the issue.

`192.168.1.255` was your broadcast IP address. That's a conflict. You can't use the broadcast address as a computer address. — Alexis Wilke, Mar 11 '21 at 05:42
I was likely using that as an example, i don't know why, but sometimes I worry about sharing the real `private IPv4` address I use for services lol. @AlexisWilke You could make an edit if you want! — FreeSoftwareServers, Mar 11 '21 at 19:03

score 0 · Accepted Answer · answered Jul 23 '19 at 11:45

I'm not 100% the issue (but it's fixed now!), but I found these two threads helpful.

From 192.168.0.146 icmp_seq=1 Destination Host Unreachable

Host unreachable and I do not get why

Basically it was one of two things:

A duplicate IP address conflict
A duplicate MAC address conflict

But, the trick was also to make sure to clear the arp cache via ip -s -s neigh flush all and/or reboot the VM/Target VM/Gateway Router.

I'm fairly certain my issue was a duplicate MAC address. I generally use disks as a template and create a new VM via the GUI and just point it to the copy of the disk template. But, I think this time I used a domain.xml and modified the disk parameter to point to the new disk. The issue was that domain.xml was still in use by the previous template VM w/ the same MAC.

No Route To Host from one VM on LAN

1 Answers1