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This is a common occurrence on my KVM server and is frustrating because just messing with networking on the server fixes the issue and I have no idea how it gets fixed.

Last night power outage from strong storms prompted this instance of it. The power went off, which means my server went down because it does not have it's redundant power supply plugged in, because it wouldn't make a difference. It's on the same circuit in my basement and is just my fun nerdy server that I host personal services on. Now, the kvm guests cannot reach the Internet normally because dns fails. One positive is that they can ping by IP address, but that doesn't help too much unfortunately.

I have most kvm servers on the br0 bridge and route the traffic rather than routing it so I can assign them static IPs on my internal network and port forward them. I have included 'ip r', and 'ip a' configuration from my kvm host, and the kvm xmldump of my unreliable as of yet mailserver.

I appreciate any help or troubleshooting directions anyone can give me. Thank you!!

default via 192.168.86.1 dev br0
169.254.0.0/16 dev br0  scope link  metric 1008
172.17.0.0/16 dev docker0  proto kernel  scope link  src 172.17.0.1
192.168.86.0/24 dev br0  proto kernel  scope link  src 192.168.86.254
192.168.100.0/24 dev virbr0  proto kernel  scope link  src 192.168.100.1
192.168.122.0/24 dev defaultbr  proto kernel  scope link  src 192.168.122.1





1: lo:  mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp3s0f0:  mtu 1500 qdisc mq master br0 state UP qlen 1000
    link/ether b4:99:ba:05:39:22 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::b699:baff:fe05:3922/64 scope link
       valid_lft forever preferred_lft forever
3: enp3s0f1:  mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether b4:99:ba:05:39:24 brd ff:ff:ff:ff:ff:ff
4: enp4s0f0:  mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether b4:99:ba:05:39:26 brd ff:ff:ff:ff:ff:ff
5: enp4s0f1:  mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether b4:99:ba:05:39:28 brd ff:ff:ff:ff:ff:ff
6: ib0:  mtu 4092 qdisc noop state DOWN qlen 256
    link/infiniband 80:00:02:08:fe:80:00:00:00:00:00:00:00:16:35:ff:ff:bf:fb:f5 brd 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff
7: ib1:  mtu 4092 qdisc noop state DOWN qlen 256
    link/infiniband 80:00:02:09:fe:80:00:00:00:00:00:00:00:16:35:ff:ff:bf:fb:f6 brd 00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff
8: br0:  mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether b4:99:ba:05:39:22 brd ff:ff:ff:ff:ff:ff
    inet 192.168.86.254/24 brd 192.168.86.255 scope global br0
       valid_lft forever preferred_lft forever
    inet6 fe80::b699:baff:fe05:3922/64 scope link
       valid_lft forever preferred_lft forever
9: defaultbr:  mtu 1500 qdisc noqueue state DOWN qlen 1000
    link/ether 52:54:00:02:c8:49 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global defaultbr
       valid_lft forever preferred_lft forever
10: defaultbr-nic:  mtu 1500 qdisc pfifo_fast master defaultbr state DOWN qlen 1000
    link/ether 52:54:00:02:c8:49 brd ff:ff:ff:ff:ff:ff
11: virbr0:  mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether 52:54:00:f8:4c:be brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.1/24 brd 192.168.100.255 scope global virbr0
       valid_lft forever preferred_lft forever
12: virbr0-nic:  mtu 1500 qdisc pfifo_fast master virbr0 state DOWN qlen 1000
    link/ether 52:54:00:f8:4c:be brd ff:ff:ff:ff:ff:ff
13: vnet0:  mtu 1500 qdisc pfifo_fast master br0 state UNKNOWN qlen 1000
    link/ether fe:54:00:3f:08:1f brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fe3f:81f/64 scope link
       valid_lft forever preferred_lft forever
14: docker0:  mtu 1500 qdisc noqueue state UP
    link/ether 02:42:22:11:f5:ab brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 scope global docker0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:22ff:fe11:f5ab/64 scope link
       valid_lft forever preferred_lft forever
18: veth776aca1@if17:  mtu 1500 qdisc noqueue master docker0 state UP
    link/ether da:8a:e2:11:8a:6f brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet6 fe80::d88a:e2ff:fe11:8a6f/64 scope link
       valid_lft forever preferred_lft forever
35: vnet1:  mtu 1500 qdisc pfifo_fast master br0 state UNKNOWN qlen 1000
    link/ether fe:54:00:c5:0f:38 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fec5:f38/64 scope link
       valid_lft forever preferred_lft forever
36: vnet2:  mtu 1500 qdisc pfifo_fast master br0 state UNKNOWN qlen 1000
    link/ether fe:54:00:3c:a8:3c brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fe3c:a83c/64 scope link
       valid_lft forever preferred_lft forever
37: vnet3:  mtu 1500 qdisc pfifo_fast master virbr0 state UNKNOWN qlen 1000
    link/ether fe:54:00:a8:a2:1e brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fea8:a21e/64 scope link
       valid_lft forever preferred_lft forever
38: vnet4:  mtu 1500 qdisc pfifo_fast master virbr0 state UNKNOWN qlen 1000
    link/ether fe:54:00:48:fa:1f brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fe48:fa1f/64 scope link
       valid_lft forever preferred_lft forever
39: vnet5:  mtu 1500 qdisc pfifo_fast master br0 state UNKNOWN qlen 1000
    link/ether fe:54:00:20:c2:ce brd ff:ff:ff:ff:ff:ff
    inet6 fe80::fc54:ff:fe20:c2ce/64 scope link
       valid_lft forever preferred_lft forever





 zimbra-centos7                                                                                                             
 aacb9a74-d5f9-48c0-8d26-481cd573bcfd                                                                                       
 8392704                                                                                                     
 8392704                                                                                       
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   /usr/libexec/qemu-kvm                                                                                            
                                                                                                         
                                                                                                       
                                                                                               
                                                                                                                          
                                                                                                         
                                                                                                                        
                                                                                                             
                                                              
                                                                                                                                  
                                                                                                        
                                                                                                         
                                                                                                                          
                                                                                                            
                                                                                                                              
                                                                                                                        
                                                                                                                 
                                                                       
                                                                                                                                  
                                                                                     
                                                                                                                      
                                                              
                                                                                                                            
                                                                                     
                                                                                                                      
                                                                                                                  
                                           
                                                                                                                            
                                                                                     
                                                                                                                      
                                                                                                                  
                                                              
                                                                                                                            
                                                                                     
                                                                                                                      
                                                                                                                  
                                                              
                                                                                                                            
                                                                                       
                                                                                                                    
                                                                                                                            
                                                                                                        
                                                                                                                      
                                                              
                                                                                                                            
                                                                                              
                                                                                                           
                                                              
                                                                                                                            
                                                                                                                
                                                                                                       
                                                                                                                   
                                                                                                                    
                                                                                                                   
                                                                                                                     
                                                              
                                                                                                                             
                                                                                                                      
                                                                                                              
                                                                                                                       
                                                                                                                  
                                                                                                                                
                                                                                                    
                                                                                                              
                                                                                                         
                                                                                                                  
                                                                                                                               
                                                                                                                    
                         
                                                               
                                                                                                                 
                                                                          
                                                                                                                               
                                                                                                                
                                                                   
                                                                                                                 
                                                                          
                                                                                                                               
                                                                                                          
                                                                                                                   
                                                                                                   
                                                                                                                                 
                                                                                                           
                                                                                                                   
                                                                                                                                 
                                                                                                        
                                                                                                                   
                                                                                                                                 
                                                                         
                                                                                               
                                                                                                                              
                                                                                                                     
                                                                                                                   
                                                              
                                                                                                                                 
                                                                                                                                  
                                                      
                                                                                                                   
                                                              
                                                                                                                                 
                                                                                                     
                                                                                                                   
                                                                                                   
                                                                                                                              
                                                                                                     
                                                                                                                   
                                                                                                   
                                                                                                                              
                                                                                                              
                                                                                                                 
                                                              
                                                                                                                            
                                                                                                                               
                                                                                  
   system_u:system_r:svirt_t:s0:c340,c568                                                                                 
   system_u:object_r:svirt_image_t:s0:c340,c568                                                                 
                                                                                                                              
                                                                                      
   +107:+107                                                                                                              
   +107:+107                                                                                                    
                                                                                                                              
                                                                                                                                 
  • 1
    I haven't messed with KVM, but sounds like something racy on startup . . . do you see the same issue if you do a graceful restart of your server? – ernie Jul 21 '17 at 17:58
  • I would agree. The workaround would be a startup script that replicates the steps you perform to restore functionality. – HackSlash Jul 21 '17 at 18:20
  • i'm rebooting it now. will reply in a minute when its back. if it's back since I am remote, lol. worse case is I let you know when I get home. – Kyle H Jul 21 '17 at 18:23
  • It came back up, just got distracted. Still no dns on the one server that I set up to automatically turn back on. – Kyle H Jul 21 '17 at 19:13
0

askubuntu.com/questions/574548/ubuntu-kvm-guest-dns-problems Flush iptables and set default to accept. Got messed up.

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