Intermittent Connectivity Issues on Random Instances

[Naoko Reeves]

I'm having intermittent connectivity issue on random instance on random occasion.

When I loose connection:

1. I'm unable to ssh nor ping but at one point this was possible to those instances so it should not be firewall issue.

2. I'm able to ssh into it from browser window

This happen to:

1. Instance w/wo static external IP

2. Just launched or log running

3. All instances happen to be us-east1-d so far

I was watching one of the instance's log and saw

```

Apr 12 15:52:32 lab-naoko sshd[910]: error: maximum authentication attempts exceeded for root from 95.6.94.248 port 36118 ssh2 [preauth]

Apr 12 15:52:32 lab-naoko sshd[910]: Disconnecting: Too many authentication failures [preauth]

```

which is not my IP

I'm not sure if this type of attempt creates temporary blockage?

Any advice would be appreciated.

[Marilu (Cloud Platform Support)]

Hello Naoko,

The SSH attempts will not block you for SSH into the instance, as you mentioned you're able to SSH from the Cloud Console.

Are you running some kind of security software(e.g. sshguard) in the server that could possibly block the connection from your local environment after many invalid attempts?

To troubleshoot this issue you can run the following tests:

- Telnet to your instance on SSH port to see if you're able to connect

- Traceroute to your instance from your local environment, to see if the traffic is being dropped at some point and in the other direction also.

- Tcpdump on the affected instance on both sides, to see if packets are being sent and rejected at the OS level. 

Note that this tests will need to be performed when you're experiencing the SSH issue. 

I hope this helps,

Marilu