Unable to connect to Cisco IOS-XR

Hi Ron,

Greetings. I am working with multiple vendor networking devices to execute commands. With the below asyncssh code, I verified connecting to Nokia, Huawei and a few models of Cisco. For some reason, I am unable to connect to Cisco ASR9K which is a IOS-XR device. It returns asyncssh.misc.ConnectionLost: Connection lost error every time.

async with asyncssh.connect(host, username=user, password=pwd, port=22,
                                known_hosts=None, kex_algs=k_algs, encryption_algs=e_algs, mac_algs=m_algs,
                                compression_algs=None, login_timeout=60, ) as conn:
        async with conn.create_process() as process:
            print('after conn')
            print("**************************%s******************************" % disable_paging_cmd)
            process.stdin.write(f'{disable_paging_cmd}\r\n')
            print("**************************%s******************************" % cmd)
            process.stdin.write(f'{cmd}\r\n')
            print("**************************%s******************************" % exit_command)
            process.stdin.write(f'{exit_command}\r\n')
            line = await process.stdout.read()
            print(str(line))

Any special cases to be handled for IOS-XR?

[ronf]

Sorry - the ValueError was my mistake. It should have been '+ssh-dss', rather than '+ssh_dss', but it looks like you figured that out.

Regarding the output hang, see if sending only ‘\r’ as the line ending works rather than ‘\r\n’. If you set a terminal type, the remote system would be expecting your terminal to only send carriage return when you hit “enter” after typing a command. Also, is the “quit” command you are sending normally enough to trigger the server to do a connection close? If not, that could explain the hang. I’m not seeing any sign of it trying to close the connection in your debug output.

[mon-216]

Hi Ron, thanks for your timely responses. After setting the host_key_algs, I had to set the term_type too. I am able to connect to IOS-XR (ASR9K) box with asyncssh now. Pasting below the options I added for someone’s reference

server_host_key_algs=['ssh-dss'], term_type='xterm-color', term_size=(80, 24)

However the issue with NCS540 (another IOS-XR) device still exists. I have the term_type set as you suggested. The Session request failed error is gone. But after opening the session, the commands are executed and the session hangs without reading any output indefinitely.

Debug logs -

DEBUG:asyncssh:[conn=0, chan=0] Set write buffer limits: low-water=16384, high-water=65536
INFO:asyncssh:[conn=0, chan=0] Requesting new SSH session
DEBUG:asyncssh:[conn=0, chan=0]   Initial recv window 2097152, packet size 32768
DEBUG:asyncssh:[conn=0, chan=0]   Initial send window 2097152, packet size 32768
DEBUG:asyncssh:[conn=0, chan=0]   Terminal type: xterm-color
DEBUG:asyncssh:[conn=0, chan=0]   Terminal size: 80x24
INFO:asyncssh:[conn=0, chan=0]   Interactive shell requested
after conn
**************************terminal length 0******************************
DEBUG:asyncssh:[conn=0, chan=0] Sending 19 data bytes
**************************show bgp neighbor******************************
DEBUG:asyncssh:[conn=0, chan=0] Sending 19 data bytes
**************************quit******************************
DEBUG:asyncssh:[conn=0, chan=0] Sending 6 data bytes
DEBUG:asyncssh:[conn=0, chan=0] Reading from channel started
DEBUG:asyncssh:[conn=0, chan=0] Received 21 data bytes
DEBUG:asyncssh:[conn=0, chan=0] Received 21 data bytes
DEBUG:asyncssh:[conn=0, chan=0] Received 8 data bytes
DEBUG:asyncssh:[conn=0, chan=0] Received 147 data bytes
DEBUG:asyncssh:[conn=0, chan=0] Received 4 data bytes
DEBUG:asyncssh:[conn=0, chan=0] Received 35 data bytes
^C

I tried changing the term_type to vt100 after checking some config docs of NCS540. But that doesn’t work either