The One-Second Answer
- All four lights solid — connected and online. Nothing to do.
- Downstream or Upstream blinking — the modem is still finding the signal. Wait, or power cycle.
- Online blinking or off — not registered with your ISP yet; this is the usual "no internet" light.
- Blue vs green — both mean connected; blue is the faster high-bonding connection.
SURFboard is the modem brand made by Arris and Motorola (models like the SB6141, SB6183, SB8200, and S33). It's a modem, not a router — so if you also have a separate router, the modem's lights must be healthy first before the router can get online. Combo SURFboard units (SBG-series "SURFboard Gateway") add Wi-Fi lights on top of these.
SURFboard Modem Light Guide
| Light | State | Meaning |
|---|---|---|
| Power | Solid green | Modem has power and has finished booting |
| Receive / Downstream (down arrow) | Blinking | Scanning for the downstream channel — not connected yet |
| Receive / Downstream | Solid green | Connected on the downstream with standard channel bonding |
| Receive / Downstream | Solid blue | Connected using high-speed bonding (more channels / DOCSIS 3.1) |
| Send / Upstream (up arrow) | Blinking | Ranging the upstream channel — connection not complete |
| Send / Upstream | Solid green | Connected on the upstream with standard bonding |
| Send / Upstream | Solid blue | High-speed upstream bonding active |
| Online (globe) | Blinking | Registering with the ISP — almost there, not online yet |
| Online (globe) | Solid green | Registered and online — internet is available |
| Any light off (with power) | — | Modem crashed or the connection dropped; reboot needed |
Rule of thumb: the lights come up in order — Power, then Downstream, then Upstream, then Online. Whichever one is still blinking is where the connection is stuck.
Green vs Blue on a SURFboard — What It Means
This one confuses a lot of people. On many SURFboard models the Downstream and Upstream lights can be either green or blue, and both mean you're connected:
- Green — connected using standard channel bonding (fewer bonded channels).
- Blue — connected using high-speed bonding across more channels (DOCSIS 3.0 with many channels, or DOCSIS 3.1 OFDM).
Blue is the better, higher-throughput state. If you pay for a fast plan (say 500 Mbps or gigabit) but the lights stay green, your modem may not be bonding the channels your plan needs — worth confirming your modem supports your tier and asking your ISP to check provisioning. See DOCSIS 3.0 vs 3.1 vs 4.0 for which modem your plan requires.
Fixing a SURFboard That Won't Come Online
Work through these in order — most "no internet" cases are solved by the first two steps:
- Check for an outage. Look in your ISP's app or outage map. A line-wide outage can't be fixed from your end.
- Power cycle the modem. Unplug it (remove any coin-cell/backup), wait 30 seconds, plug it back in, and wait up to 5 minutes for the Online light to go solid.
- Check the coax. The coaxial cable into the modem must be finger-tight at both ends. A loose connector or a splitter in the line is a common cause of blinking downstream/upstream lights.
- Reboot the router too. If you have a separate router, only reboot it after the modem's Online light is solid — see how to restart your router in the right order.
- Read the signal levels. Open the modem's status page (below) and check downstream/upstream power and SNR. Values far out of range point to a line fault to report.
- Call your ISP. If the Online light never goes solid after reboots and the coax is tight, the modem may need re-provisioning or there's a signal problem on the line.
Check Your SURFboard Signal Page
Every SURFboard modem has a built-in status page that loads even with no internet, because it's served by the modem itself. Connect a device to the modem and open it in a browser:
- Most SURFboard modems: 192.168.100.1
- Some Comcast/Xfinity-provisioned SURFboard units: 10.0.0.138
The Connection or Signal page shows downstream power (aim for roughly −7 to +7 dBmV), SNR (35 dB or higher), and upstream power (35–50 dBmV), plus error counts. Screenshot these before calling your ISP — it turns the call into a fact-based conversation instead of "have you restarted it."
Common SURFboard Light Scenarios
Downstream light blinking and never goes solid
The modem can't lock onto the signal coming in. Tighten the coax, remove any unnecessary splitters, and power cycle. If it persists, the line signal is likely too weak — an ISP issue.
All lights solid but no internet on devices
If Online is solid green but nothing loads, the problem is past the modem — your router, Wi-Fi, or a single device. See Wi-Fi connected but no internet.
Lights keep dropping and re-syncing
A connection that repeatedly loses the Online light usually means an intermittent signal fault, a bad cable, or a failing modem. If reboots don't hold, see internet keeps dropping and ask your ISP to check your levels.
Frequently Asked Questions
Why is my SURFboard downstream light blue instead of green?
Both mean you're connected. Green is standard channel bonding; blue is high-speed bonding across more channels (or DOCSIS 3.1). Blue is the faster state — if you're on a fast plan but stuck on green, ask your ISP to check provisioning.
What lights should be on for a SURFboard modem to work?
Solid Power, Downstream, Upstream, and Online. Any of the middle three blinking means it hasn't finished connecting, and the Online light must be solid before your devices get internet.
Why does my SURFboard Online light keep blinking?
It's registering but not fully connected. Power cycle the modem, make sure the coax is finger-tight, and wait up to 5 minutes. If it never goes solid, it's usually a line/signal problem or an outage.
How do I check SURFboard signal levels?
Open 192.168.100.1 (or 10.0.0.138 on some Comcast units) in a browser while connected to the modem, and read the Connection/Signal page.