Send command with changing prompt

[SoerenBusse]

Hey there,

we’re trying to use Netmiko with Huawei SmartAX devices. These devices have the peculiarity that certain interface-specific display commands must be run from within the corresponding interface configuration context.

Here’s an example:

enable
config
interface mpu 0/8
display port ddm-info 0

The simplest approach we’ve found with Netmiko looks like this:

net_connect = ConnectHandler(
    device_type="huawei_smartax",
    host="<host>",
    username="<user>",
    password="<password>"
)

net_connect.enable()
net_connect.config_mode()

net_connect.send_command("interface mpu 0/8")
result = net_connect.send_command("display port ddm-info 0")

net_connect.disconnect()

print(result)

However, this results in a read timeout, due to the way send_command attempts to detect the prompt:

1. _prompt_handler is called, which in turn calls find_prompt (when auto_find_prompt=True, the default).
2. It sends a RETURN and extracts the resulting prompt.
3. At this point, the prompt is HOSTNAME(config)#, which _prompt_handler returns to send_command and stores as search_pattern.
4. The command is then executed, which changes the prompt to 49_441_1893_76Z4(config-if-mpu-0/8)#.
5. Since the search_pattern no longer matches the new prompt, a ReadTimeout is raised.

We’ve identified two potential workarounds:

• Set auto_find_prompt=False, which makes Netmiko look only for the base_prompt. But since the base prompt is usually just the hostname, this can cause issues if the command output also includes the hostname (Netmiko may interpret it as the prompt).
• Use expect_string with a regex such as HOSTNAME(>|#|(.*)#).

Both approaches work, but they feel more like hacks than proper solutions.

What is the recommended way to use send_command when the command itself changes the device prompt?

[ktbyers]

The typical pattern for situations similar to what you described are to use the expect_string argument and a terminating reg-ex pattern.