Requesting Modem Support

Requesting Modem Support

Before opening a modem support request, please follow this guide to collect the data we need. Building a driver for a new modem requires understanding how its web interface communicates -- every manufacturer and even every ISP firmware variant can use completely different APIs. A HAR capture gives us that information without guesswork.

For modems with login-protected web UIs, a useful HAR capture must include the actual login exchange, not only requests made after you are already logged in.

Step 1: Prepare a Clean Capture

Before recording:

• Close any already-open browser tabs to the modem web UI
• If possible, start from a known clean state (for example right after reboot, or after confirming no active modem UI session is open in another tab)
• If you are debugging login or polling problems, enable DOCSight debug logging before testing

Common modem web interface addresses:

• http://192.168.0.1
• http://192.168.100.1
• http://192.168.178.1
• https://192.168.0.1 (some modems use HTTPS)

If you run your modem in bridge mode, the address might be different. Check the label on your modem or your ISP's documentation.

Step 2: Find the DOCSIS Status Page

Navigate to the page that shows your downstream and upstream channel data. This page typically shows a table with columns like frequency, power level, SNR/MER, modulation, and error counts. The exact location varies by modem:

• Arris: Status -> Connection
• Netgear: Cable Connection
• Sagemcom: Internet Connectivity -> DOCSIS -> RF Parameters
• Technicolor/Compal: Status -> DOCSIS WAN

Step 3: Capture a HAR File

A HAR (HTTP Archive) file records all network traffic between your browser and the modem. This shows us the exact API endpoints, authentication flow, request bundling, session behavior, and response format.

Important: start recording before opening the modem web interface, so the HAR includes the initial page load and the login flow itself.

Chrome

1. Press F12 to open Developer Tools
2. Click the Network tab
3. Make sure recording is active (red dot in the top left)
4. Check Preserve log so navigation doesn't clear the list
5. Start recording before opening the modem web interface
6. Open the modem web UI in a clean tab
7. Log in
8. Navigate to the DOCSIS status page
9. Wait for the page to fully load
10. Right-click anywhere in the request list -> Save all as HAR with content

Firefox

1. Press F12 to open Developer Tools
2. Click the Network tab
3. Check Persist Logs (gear icon)
4. Start recording before opening the modem web interface
5. Open the modem web UI in a clean tab
6. Log in
7. Navigate to the DOCSIS status page
8. Wait for the page to fully load
9. Click the gear icon -> Save All As HAR

Verify the HAR Before Uploading

Please check that the capture includes:

• The first request to the modem web UI
• The login request and response flow, if authentication is required
• The first successful requests that load channel or modem data

A capture that only contains post-login API requests is often not enough to debug login, HMAC authentication, or session lifecycle issues.

GitHub may reject raw .har uploads. If that happens, rename the file to .har.txt or upload it as a .zip archive instead.

Step 4: Redact Sensitive Data

This is important. The HAR file may contain passwords, session tokens, MAC addresses, serial numbers, or IP addresses. Open the file in a text editor and search for:

• Your modem password (replace with REDACTED)
• MAC addresses like AA:BB:CC:DD:EE:FF (replace with 00:00:00:00:00:00)
• Serial numbers (replace with REDACTED)
• Your public IP address if visible (replace with 0.0.0.0)

Session tokens and cookies are usually fine to leave in. They normally expire quickly and only work on your local network.

Step 5: Take a Screenshot

Take a screenshot of the DOCSIS status page showing the channel table. This helps us understand the visual layout and verify our parsing matches what you see.

Again, redact any MAC addresses, serial numbers, or public IPs visible in the screenshot.

Step 6: Find Your Firmware Version

Look for a "Device Info", "About", or "Status" page in the modem's web interface. Note down:

• Model number (e.g., F@st 3896, CM3000, TC4400)
• Firmware/software version (e.g., LG-RDK_6.9.35, V1.02.06)
• Hardware version if shown

The firmware version matters because ISPs ship custom firmware builds that can change the API entirely. The same modem model from two different ISPs might need completely different drivers.

Step 7: Capture Supporting Context

If the issue involves login failures, polling failures, empty data, or session conflicts, also collect:

• DOCSight debug logs from the same test window
• Whether the modem UI was open in another browser tab at the same time
• Whether the problem happens on the first login, after a poll cycle, or only when browser access happens in parallel
• Whether the modem was freshly rebooted before the test

Step 8: Open the Issue

Go to New Modem Support Request and fill in the form. Attach your redacted HAR capture, screenshot, and any relevant debug logs.

Why We Need All This

Cable modem web interfaces are not standardized. Some use REST APIs with JSON, some embed data as JavaScript variables in HTML pages, some require encrypted authentication with device-specific keys, and some enforce their own session rules. The same modem model can behave differently depending on which ISP firmware it runs. Without a HAR capture, we'd have to guess how the API works, and there are too many possible variations to get it right without seeing the actual traffic.

Troubleshooting

"I can't access the modem web interface"
If your modem is in bridge mode, it might only be reachable on a secondary IP (often 192.168.100.1). Some modems need you to be connected directly via Ethernet rather than Wi-Fi.

"The HAR file is very large"
That's normal. Modem web interfaces sometimes load many small resources. Upload it as .har.txt or .zip if needed.

"My HAR says it was captured during login, but support still says login is missing"
The relevant part is the actual login request/response flow. Some captures start too late and only include post-login API calls. Please make sure recording starts before the modem UI is opened.

"My modem doesn't show a DOCSIS status page"
Some ISP firmware hides the detailed DOCSIS channel data from users. Mention this in the issue -- there might be alternative ways to access the data (SNMP, hidden pages, etc.).