The problem was related to MTU.
Actually, I have another installation which is configured to set 1450(1500 - 50 
VxLAN header length) for guest VM interfaces.
That setup runs in 'regular' network environments with 1500 MTU on host 
interfaces  and use linuxbridge.

There is a reson why I didn't looked at that at first thing for the current 

The hosts private network interfaces  has set to MTU 9000 
Open vSwitch is used to connect private(self service) network.
OVS bridges have 1500 MTU ( kolla configured it in this way )

I've identified that  1480  MTU for guest VM fix ssh issue  in my current case, 
but not sure I understand why ...
20 bytes is the shortest IP header size...

So there are 2 another questions:
1. What's and why adding 20 bytes ? 
2. I've not found a configuration settings in kolla-ansible which allows to 
configure bridges interfaces MTU - any ideas how to do that properly ?


06.04.2018, 20:57, "Brian Haley" <haleyb....@gmail.com>:
> On 04/06/2018 01:28 PM, s serge wrote:
>>  Hello,
>>  I'm evaluating an installation and everything from networking side was 
>> looking good
>>  until I tried to reach a VM host via private network from another VM via 
>> ssh.
>>  In short:
>>  1. Spawn a VM
>>  2. Associate a floating IP
>>  3. Logon to VM via ssh on public network
>>  4. Spawn another VM
>>  5. Try to reach 1st VM via ssh private network IP - FAIL.
>>  6. ICMP to 1st VM IP via private network works well.
>>  Looks pretty weird for me as according to logs everything looks fine,
>>  both VM got assigned a private IP and fetches metadata info.
>>  Some notes about setup:
>>  Separate interfaces for management, private(VXLAN) and external network.
>>  Dozen of similar servers.
>>  I'll continue to debug the issue, but appreciate any relevant feedback.
> I would check two things:
> 1. Security groups are allowing port 22
> 2. MTU is set correctly, should probably be 1450 if you're using VXLAN,
> which should have been set via the DHCP reply
> -Brian

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