The ARRIS SURFboard S33 is a standalone DOCSIS 3.1 cable modem built for gigabit and multi-gig cable internet plans. It replaces the modem you are renting from Xfinity, Cox, or Spectrum, and connects to any Wi-Fi router or mesh system you already own. This is a modem only: it has no built-in Wi-Fi and no telephone support.
The S33 is approved for use with Comcast Xfinity, Cox, and Charter Spectrum, and works on a number of smaller cable systems as well. It is a cable modem, so it needs a coax connection from a cable internet provider.
The S33 will not work with: AT&T, Verizon Fios, CenturyLink, Frontier, Brightspeed, or any other DSL, fiber, or satellite service. It also will not work on a plan that bundles digital voice through the modem, because the S33 has no telephone port. If you have cable phone service through your provider, you need a telephony modem instead.
Approved device lists change without notice, and some plan speeds are excluded even on supported providers. Confirm the S33 against your provider's current device list before you order.
This matters more than anything else on this page if you are with Xfinity. The S33 is listed by Xfinity as a Recommended device and handles their download tiers well, but it is not on Xfinity's approved list for Next Gen mid-split upload speeds. If you are on a plan that advertises upload speeds in the hundreds of megabits, such as Gigabit X2 or another Next Gen tier, the S33 will hold your downloads at full speed while capping your uploads at the older, slower rate.
If that describes your plan, look at the ARRIS S34 instead, which is on Xfinity's Next Gen list. If you are on a standard Xfinity plan where upload is 35 Mbps or similar, the S33 is a strong fit and this limitation will not affect you. Our Xfinity compatible modems list by speed tier breaks down which modems match which plans.
Renting a gateway is the most expensive way to get a modem. Current equipment charges look like this:
On Xfinity or Cox, a purchased modem typically pays for itself inside a year and then keeps saving every month after that. On Spectrum the case is different: you are buying for performance and control rather than to erase a modem line item. Equipment fees change, so check your current bill for the exact charge.
DOCSIS 3.1 is the current cable standard on retail modems. It adds OFDM channels, which are wider and more efficient carriers than the older SC-QAM channels, and that is what makes speed tiers above 1 Gbps possible over coax. The S33 runs 2 downstream and 2 upstream OFDM channels alongside 32 x 8 DOCSIS 3.0 bonded channels, so it negotiates whichever standard your provider has deployed in your area and falls back cleanly to 3.0 where 3.1 has not landed yet.
One thing worth being clear about: your modem does not create speed. It removes a ceiling. A DOCSIS 3.1 modem on a 300 Mbps plan delivers 300 Mbps, the same as a good DOCSIS 3.0 modem would. What you gain is headroom for the plan upgrades your provider rolls out later, plus better performance under congestion.
The back panel has one 2.5 Gbps Ethernet port and one 1 Gbps Ethernet port. The 2.5 Gbps port is the one you want feeding your router or mesh system, since a 1 Gbps port would bottleneck any plan faster than gigabit before the traffic ever reached your network.
The two ports do not combine. The S33 does not support link aggregation, so you cannot bond them into a single 3.5 Gbps connection. The second port operates as an independent connection, and most providers require an additional IP address on your account to use both at once. Check with your provider before planning a build around the second port.
Connect coax to the wall outlet, plug in the power adapter, and run an Ethernet cable from the 2.5 Gbps port to your router's WAN port. Give the modem a few minutes to pull its configuration file and sync with the network, then activate it with your provider using the SURFboard Central app, your provider's app, or a phone call with the modem's MAC address and serial number from the label on the bottom.
The modem's own status page lives at 192.168.100.1 and shows signal levels, channel lock status, and firmware version, which is where to look first if something is not working.
The S33 has a single status LED under the SURFboard logo rather than the row of lights on older modems:
A steady green light is not a fault. It means your provider has you on a DOCSIS 3.0 channel plan in that area, and the modem will move to 3.1 when they deploy it.
| Feature | ARRIS S33 | ARRIS S34 | ARRIS SB8200 | ARRIS G36 |
|---|---|---|---|---|
| DOCSIS version | 3.1 | 3.1 | 3.1 | 3.1 |
| Rated download | Up to 2.5 Gbps | Up to 2.5 Gbps | Up to 2 Gbps | Up to 2.5 Gbps |
| Channel bonding | 32 x 8 plus 2x2 OFDM | 32 x 8 plus 2x2 OFDM | 32 x 8 plus 2x2 OFDM | 32 x 8 plus 2x2 OFDM |
| Ethernet ports | 1 x 2.5 Gbps, 1 x 1 Gbps | 1 x 2.5 Gbps, 1 x 1 Gbps | 2 x 1 Gbps | 1 x 2.5 Gbps, 4 x 1 Gbps |
| Built-in Wi-Fi router | No | No | No | Yes, Wi-Fi 6 AX3000 |
| Xfinity Next Gen upload tiers | Not approved | Approved | Not approved | Approved |
| Voice or telephone service | No | No | No | No |
| Provider compatibility | Cox, Spectrum, Xfinity | Cox, Spectrum, Xfinity | Cox, Spectrum, Xfinity | Cox, Spectrum, Xfinity |
| Best for | Standard gigabit plans where upload is not mid-split | Next Gen or enhanced upload plans | Plans up to 1 Gbps on a tighter budget | One device instead of a modem plus router |
The S33 and S34 are close relatives with the same channel layout, the same port configuration, and the same 2.5 Gbps ceiling. The S34 is the newer flagship and adds switchable upstream filters for next generation upload tiers. If your provider has not deployed enhanced uploads in your area, the two perform the same.
A coax cable is not included. Most homes already have one at the wall outlet.
No. The S33 is a modem only. You connect it to your own Wi-Fi router or mesh system with an Ethernet cable. If you want one device that does both, look at a modem router combo like the ARRIS G36 instead.
No. The S33 has no telephone port and does not support cable digital voice service. If you have phone service bundled through your provider, you need a telephony modem such as an ARRIS TM or TG series unit.
Not on Next Gen or mid-split enhanced upload plans. Xfinity has not approved the S33 for those tiers, so your uploads will run at the standard rate even if your plan advertises higher. Download speeds are unaffected. The ARRIS S34 is approved for those tiers.
Not today, but it costs you nothing to have it. Use the 1 Gbps port or the 2.5 Gbps port, either works fine at 500 Mbps. The faster port matters when you upgrade past gigabit.
Sometimes, but they cannot be combined into one faster connection. The S33 has no link aggregation. Using both ports at once generally requires your provider to issue a second IP address on your account.
It is approved for Cox and Spectrum, and works on several other cable systems. Since approved device lists are updated regularly and some speed tiers are excluded, check your provider's current list before ordering.
No. Those are DSL and fiber services and need an entirely different type of modem or ONT. The S33 is a cable modem and requires a coax connection from a cable provider.
Green means the modem is connected and working in DOCSIS 3.0 mode, which is what your provider has deployed in your area. It is not an error, and the modem will switch to 3.1 automatically when the upgrade reaches you.
New to the S33? Our step-by-step manual covers installation, activation, admin login at 192.168.100.1, Wi-Fi and bridge mode guidance, and fixes for the most common issues.
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