paramiko.ssh_exception.SSHException: Error reading SSH protocol banner when the router is down via SSH tunnel

Hi,

I am connecting to a device via ssh tunnel just fine. During a reload, I am getting the following traceback:

Exception: Error reading SSH protocol banner Traceback (most recent call last): File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/transport.py", line 2211, in _check_banner buf = self.packetizer.readline(timeout) File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/packet.py", line 380, in readline buf += self._read_timeout(timeout) File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/packet.py", line 622, in _read_timeout raise socket.timeout() socket.timeout `During handling of the above exception, another exception occurred:` Traceback (most recent call last): File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/transport.py", line 2039, in run self._check_banner() File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/transport.py", line 2215, in _check_banner raise SSHException( paramiko.ssh_exception.SSHException: Error reading SSH protocol banner

Since it’s part of try/except, the script doesn’t break. I’m having hard time with paramiko “establishing” ssh connection to a device that is down and throwing the stack backtrace. When the router comes up the connection is established just fine. Here is the output of the debug:

DEBUG:paramiko.transport:starting thread (client mode): 0xdd2bb80 DEBUG:paramiko.transport:Local version/idstring: SSH-2.0-paramiko_2.7.1 ERROR:paramiko.transport:Exception: Error reading SSH protocol banner ERROR:paramiko.transport:Traceback (most recent call last): ERROR:paramiko.transport: File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/transport.py", line 2211, in _check_banner ERROR:paramiko.transport: buf = self.packetizer.readline(timeout) ERROR:paramiko.transport: File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/packet.py", line 380, in readline ERROR:paramiko.transport: buf += self._read_timeout(timeout) ERROR:paramiko.transport: File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/packet.py", line 622, in _read_timeout ERROR:paramiko.transport: raise socket.timeout() ERROR:paramiko.transport:socket.timeout ERROR:paramiko.transport: ERROR:paramiko.transport:During handling of the above exception, another exception occurred: ERROR:paramiko.transport: ERROR:paramiko.transport:Traceback (most recent call last): ERROR:paramiko.transport: File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/transport.py", line 2039, in run ERROR:paramiko.transport: self._check_banner() ERROR:paramiko.transport: File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/paramiko/transport.py", line 2215, in _check_banner ERROR:paramiko.transport: raise SSHException( ERROR:paramiko.transport:paramiko.ssh_exception.SSHException: Error reading SSH protocol banner ERROR:paramiko.transport: Connect to 9.0.6.202 failed

The code: try: net = ConnectHandler(**lab) print(f"““Connected to {lab[“ip”]}\n””“) prompt = net.find_prompt() except: print(f”““Connect to {lab[“ip”]} failed\n””") exit()

I have followed paramiko’s posts regarding this exception and patched proxy.py and transport.py accordingly, but neither of the cases was referring to a device down case.

Thanks

[ciscorat]

just saw your answer. I’ll try something different.

Thanks!

[ktbyers]

I am going to close as I don’t think there is anything else to do here.