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I have two VMs on a Ubuntu KVM host — and uat.example. I can ping and SSH to my UAT server but I can't SSH to my WWW server even though I can ping it. The only thing that is different between the two VMs is the IP group.

  • The IP of the UAT server is:
  • The IP of the WWW server is:
  • The IP of the host KVM server is:

There's a bridge on the host KVM server through which all connections pass.

Here's my /etc/network/interfaces file:

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet manual

# The primary bridge interface
auto br0
iface br0 inet static
      bridge_ports eth0
      bridge_stp on
      bridge_fd 0
      bridge_maxwait 0

Here's the output of the links on KVM:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether bc:ae:c5:07:0e:d3 brd ff:ff:ff:ff:ff:ff
3: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
    link/ether bc:ae:c5:07:0e:d3 brd ff:ff:ff:ff:ff:ff
4: virbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
    link/ether 1e:85:05:ba:0e:2e brd ff:ff:ff:ff:ff:ff
10: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 500
    link/ether fe:16:36:77:d0:17 brd ff:ff:ff:ff:ff:ff
16: vnet2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 500
    link/ether fe:16:36:06:4d:ba brd ff:ff:ff:ff:ff:ff
17: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 500
    link/ether fe:16:36:cb:8c:44 brd ff:ff:ff:ff:ff:ff

Here are my default routes on the KVM: dev br0  proto kernel  scope link  src dev virbr0  proto kernel  scope link  src
default via dev br0  metric 100

I know that something is wrong here because when I do a traceroute from the host server to the UAT server, I get too many hops:

traceroute to (, 30 hops max, 60 byte packets
 1 (  4.245 ms  4.400 ms  4.388 ms
 2  * * *
 3  * * *
28  * * *
29  * * *
30  * * *

I can't seem to figure out this issue but if one of you could help me out, I'd be really grateful. I confident that this due to the network configuration in the KVM virtual bridge.


share|improve this question

If you can ping it it means there is tcp connectivity ; packet can reach the destination and traverse back -- which is good.

Now just test if there is ssh service listening.

telnet server.ip 22

you should get something like

Trying someIPaddress...
Connected to thatIPaddress.
Escape character is '^]'.
SSH-2.0-OpenSSH_X.Y YourDistro

if that does not happen; there is chance that - service is not active on destination host - service is filtered

Nmap can help you to detect if service is filtered; but at this point my bet would be you don't have openssh-server installed on those hosts; just ssh client.

You can also check on those systems with something

netstat -nlp | grep ssh 


lsof -i -n  |grep ssh | grep LISTEN

if the service is active and listening...

share|improve this answer
SSH is working on that machine because I can use Putty on my desktop to connect to it. It's only a problem when I try to SSH from from the host machine to that particular VM. – Mridang Agarwalla Aug 30 '11 at 5:11

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