feat: salvage network diagnostics skills (#1731)

2026-05-19 23:33:07 +08:00 · 2026-05-11 08:33:00 -04:00
parent df32d6bea8
commit d2ade249f6
12 changed files with 522 additions and 13 deletions
--- a/skills/netmiko-ssh-automation/SKILL.md
+++ b/skills/netmiko-ssh-automation/SKILL.md
@@ -0,0 +1,173 @@
+---
+name: netmiko-ssh-automation
+description: Safe Python Netmiko patterns for read-only collection, bounded batch SSH, TextFSM parsing, guarded config changes, timeouts, and network automation error handling.
+origin: community
+---
+
+# Netmiko SSH Automation
+
+Use this skill when writing or reviewing Python automation that connects to
+network devices with Netmiko. Keep the default path read-only; config changes
+need a separate change window, peer review, and rollback plan.
+
+## When to Use
+
+- Collecting `show` command output across routers, switches, or firewalls.
+- Building a small audit script for interface, routing, or config evidence.
+- Adding timeouts and exception handling to network SSH scripts.
+- Parsing command output with TextFSM when a template exists.
+- Reviewing automation before it touches production devices.
+
+## Safety Defaults
+
+- Start with read-only `send_command()` collection.
+- Keep inventory small and explicit; do not sweep whole address ranges.
+- Use environment variables, a vault, or `getpass`; never hardcode credentials.
+- Set connection and read timeouts.
+- Limit concurrency so older devices are not overloaded.
+- Require an explicit operator flag before `send_config_set()`.
+- Do not call `save_config()` until the change has been verified and approved.
+
+## Read-Only Connection Pattern
+
+```python
+import os
+from getpass import getpass
+from netmiko import ConnectHandler
+from netmiko.exceptions import (
+    NetmikoAuthenticationException,
+    NetmikoTimeoutException,
+    ReadTimeout,
+)
+
+device = {
+    "device_type": "cisco_ios",
+    "host": "192.0.2.10",
+    "username": os.environ.get("NETMIKO_USERNAME") or input("Username: "),
+    "password": os.environ.get("NETMIKO_PASSWORD") or getpass("Password: "),
+    "secret": os.environ.get("NETMIKO_ENABLE_SECRET"),
+    "conn_timeout": 10,
+    "auth_timeout": 20,
+    "banner_timeout": 15,
+    "read_timeout_override": 30,
+}
+
+try:
+    with ConnectHandler(**device) as conn:
+        if device.get("secret") and not conn.check_enable_mode():
+            conn.enable()
+        output = conn.send_command("show ip interface brief", read_timeout=30)
+        print(output)
+except NetmikoAuthenticationException:
+    print("Authentication failed")
+except NetmikoTimeoutException:
+    print("SSH connection timed out")
+except ReadTimeout:
+    print("Command read timed out")
+```
+
+Use placeholder addresses from documentation ranges in examples. Keep real
+inventory in an ignored local file or a secrets-managed system.
+
+## Batch Collection
+
+```python
+from concurrent.futures import ThreadPoolExecutor, as_completed
+from typing import Any
+
+def collect_show(device: dict[str, Any], command: str) -> dict[str, Any]:
+    host = device["host"]
+    try:
+        with ConnectHandler(**device) as conn:
+            output = conn.send_command(command, read_timeout=45)
+        return {"host": host, "ok": True, "output": output}
+    except (NetmikoAuthenticationException, NetmikoTimeoutException, ReadTimeout) as exc:
+        return {"host": host, "ok": False, "error": type(exc).__name__}
+
+results = []
+with ThreadPoolExecutor(max_workers=8) as pool:
+    futures = [pool.submit(collect_show, device, "show version") for device in devices]
+    for future in as_completed(futures):
+        results.append(future.result())
+```
+
+Keep `max_workers` low unless the device estate and AAA systems are known to
+handle higher connection volume.
+
+## Structured Parsing
+
+Netmiko can ask TextFSM, TTP, or Genie to parse supported command output. Treat
+parser output as an optimization, not the only evidence path.
+
+```python
+with ConnectHandler(**device) as conn:
+    parsed = conn.send_command(
+        "show ip interface brief",
+        use_textfsm=True,
+        raise_parsing_error=False,
+        read_timeout=30,
+    )
+
+if isinstance(parsed, str):
+    print("No parser template matched; store raw output for review")
+else:
+    for row in parsed:
+        print(row)
+```
+
+If parsing drives a blocking decision, keep the raw command output alongside
+the parsed result so an operator can inspect mismatches.
+
+## Guarded Config Pattern
+
+```python
+import os
+
+commands = [
+    "interface GigabitEthernet0/1",
+    "description CHANGE-1234 UPLINK-TO-CORE",
+]
+
+apply_changes = os.environ.get("APPLY_NETWORK_CHANGES") == "1"
+
+if not apply_changes:
+    print("Dry run only. Candidate commands:")
+    print("\n".join(commands))
+else:
+    with ConnectHandler(**device) as conn:
+        conn.enable()
+        before = conn.send_command("show running-config interface GigabitEthernet0/1")
+        output = conn.send_config_set(commands)
+        after = conn.send_command("show running-config interface GigabitEthernet0/1")
+        print(before)
+        print(output)
+        print(after)
+        print("Verify behavior before saving startup config.")
+```
+
+Saving the config is a separate approval step. In production, include a rollback
+snippet and capture before/after evidence in the change record.
+
+## Review Checklist
+
+- Does the script identify an explicit inventory source?
+- Are credentials absent from source, logs, and exception messages?
+- Are `conn_timeout`, `auth_timeout`, and command `read_timeout` set?
+- Are failures reported per device without stopping the whole batch?
+- Does the script avoid broad scans and unbounded concurrency?
+- Are config changes behind a dry-run or explicit operator flag?
+- Is `save_config()` separate from the initial push and tied to verification?
+
+## Anti-Patterns
+
+- Hardcoding passwords, enable secrets, or private keys in source.
+- Sending config commands as the default code path.
+- Running automation against a CIDR range instead of a reviewed inventory.
+- Logging full running configs to shared systems without sanitization.
+- Treating parser success as proof that the device state is correct.
+
+## See Also
+
+- Skill: `cisco-ios-patterns`
+- Skill: `network-config-validation`
+- Skill: `network-interface-health`