200-901 cheat sheet: one-page reference
This is a one-page 200-901 reference for the night before: the exam format, HTTP status codes, authentication, Python requests, Git, Docker, bash, the Cisco platforms and the common ports. It does not replace the domain guides; it is the list you reread to check what you still remember.
Exam facts
| Duration | 120 minutes |
| Questions and passing score | Not published |
| Price | 300 USD at time of writing |
| Languages | English, Japanese |
| Validity | 3 years |
Domains: Software Development and Design 15%, APIs 20%, Cisco Platforms and Development 15%, Application Deployment and Security 15%, Infrastructure and Automation 20%, Network Fundamentals 15%.
HTTP
| Code | Meaning |
|---|---|
| 200 | OK |
| 201 | Created (usual reply to a successful POST) |
| 204 | No content (successful DELETE) |
| 301 / 302 | Redirect |
| 400 | Bad request, malformed body or parameters |
| 401 | Not authenticated |
| 403 | Authenticated but not allowed |
| 404 | Not found |
| 409 | Conflict |
| 429 | Too many requests, rate limited |
| 500 / 502 / 503 | Server error, bad gateway, unavailable |
Methods: GET read, POST create, PUT replace, PATCH change part, DELETE remove. GET, PUT and DELETE are idempotent; POST is not.
Authentication: basic = base64 of user:password in an Authorization header; bearer or custom token = a token in a header; API key = a key in a header or query string.
Python
import requests
r = requests.get(url, headers=h, params=p, timeout=10)
r.raise_for_status()
data = r.json()
JSON object becomes a dict, array a list. json.loads parses text, json.dumps writes it. yaml.safe_load parses YAML. unittest tests subclass TestCase and use assertEqual.
Git
clone, add, rm, commit, push, pull, branch, checkout or switch, merge, diff. A conflict shows markers (<<<<<<<, =======, >>>>>>>); edit, add, then commit. In a unified diff, - lines are removed, + lines are added.
Docker and bash
Dockerfile: FROM base, RUN build step, COPY files, EXPOSE port, CMD start command. docker build -t name ., docker run -p host:container name. Bash: pwd, ls, cd, mkdir, cp, mv, rm, chmod, export VAR=value, env.
Cisco platforms
| Platform | Remember |
|---|---|
| Meraki | Cloud dashboard API; organizations, networks, devices; key in header |
| Catalyst Center | Token from an auth call, then X-Auth-Token; device list under the intent API |
| ACI | APIC REST API with managed objects |
| Catalyst SD-WAN | Controller API with a session token |
| NSO | Service orchestration with YANG models, RESTCONF and NETCONF |
| UCS Manager / Intersight | On-premises compute / cloud compute management |
| Webex | REST API; spaces, memberships, messages; bearer token |
| CUCM | AXL (SOAP, configuration) and UDS (REST, user data) |
| IOS XE / NX-OS | NETCONF, RESTCONF, YANG; NX-OS also offers NX-API |
Ports and services
SSH 22, Telnet 23, DNS 53, DHCP 67/68, HTTP 80, NTP 123, SNMP 161, HTTPS 443, NETCONF 830 (over SSH). RESTCONF runs over HTTPS. Planes: management, control, data.
Automation tools
Ansible: agentless, YAML playbooks, push-based. Terraform: declarative infrastructure as code with a plan and apply. NSO: network service orchestrator. CML: network simulation. pyATS: network test automation. CI/CD: build, test, deploy.
Start with the study plan if you are not near ready, or test yourself with the practice test.