Why is cable internet speed slower than Wi-Fi? Technical reasons and solutions

You connected your computer to the router via Ethernet cable, expecting maximum speed, but tests show results worse than expected Wi-FiThis isn't uncommon—about 15% of users encounter this problem, despite the fact that a wired connection should theoretically be more stable and faster. What's going on?

The reasons may lie in hardware limitations (cable, port, network card), and in software settings (drivers, protocol, traffic prioritization). In this article, we will discuss 7 Key Factors Why Cable Connections Are Worse Than Wireless, and we'll provide a diagnostic checklist. Important: Some problems can be resolved in 5 minutes, while others require hardware replacement.

We'll start with the most obvious—checking the physical connection—and then move on to fine-tuning your router and operating system. If you're not a techie, don't worry: we'll explain everything in plain language, without unnecessary jargon.

1. Cable: type, length and damage

The first thing you need to check is yourself Ethernet cableEven if it appears intact, the internal conductors could have been damaged by kinks or strain. This is especially true for inexpensive, unshielded cables.

Cable type directly affects speed:

• 🔌 Cat 5e — up to 1 Gbit/s at a distance of up to 100 m (the most common option)
• 🔌 Cat 6/6a — up to 10 Gbit/s, but only for lengths up to 55 m (for 10G)
• 🔌 Cat 7/8 — up to 40 Gbps, but requires special connectors (overkill for home networks)

If your cable is over 10 years old or is labeled as Cat 5 (without the letter "e"), it is physically incapable of transmitting speeds higher than 100 Mbps.

Cable length This is also important: beyond 100 meters, the signal begins to fade and the speed drops. The optimal length for a home network is up to 30 meters. If the cable is laid near sources of interference (for example, near electrical wiring), speed may decrease even over short distances.

⚠️ Attention: If the cable runs through walls or ceilings, check it for fractures — they often occur at the points where the staples are attached. Use a cable tester (costs about 500 rubles) or connect the cable to another device to check.

2. Router and network card port restrictions

Even if the cable supports gigabit speeds, router ports or network card computers may be outdated. For example:

• 🖥️ Ports 10/100 Mbps (they are often not marked, but they are easily identified by their maximum speed of 100 Mbps)
• 🖥️ Ports 10/100/1000 Mbps (gigabit, marked as Gigabit Ethernet)
• 🖥️ Ports 2.5G/5G/10G (found in high-end routers and server cards)

How to check:

1. Connect the cable to another port on the router (sometimes one port works in a reduced mode).
2. Go to Control Panel → Network Adapters (Windows) or System Preferences → Network (macOS) and see your current connection speed.
3. If it is indicated there 100 Mbps, and not 1.0 Gbps, the problem is in the port or cable.

If your router or network card is limited to 100 Mbps, and Wi-Fi is working at standard 802.11ac (up to 1.3 Gbps) or Wi-Fi 6 (up to 9.6 Gbps), the difference in speed becomes obvious.

3. Router settings: Wi-Fi prioritization and QoS

Many routers prioritize by default wireless clients, especially if the function is enabled QoS (Quality of Service). This is done to improve streaming video, gaming, and video calling over Wi-Fi, but may artificially limit the speed of cable connections.

How to check the settings:

1. Go to the router's web interface (usually at 192.168.0.1 or 192.168.1.1).
2. Find the section QoS, Bandwidth Control or Traffic prioritization.
3. Check if there are any restrictions in place LAN ports (cable customers).

Also check if the mode is turned on Green Ethernet (Power Saving), which can reduce port speeds under low load. Disable it in your router settings if available.

⚠️ Attention: On some routers (for example, Keenetic) there is a function Adaptive QoS, which automatically distributes traffic. If it's enabled, try disabling it during the speed test.

4. Network card drivers and settings

Outdated or incorrectly installed network card drivers may limit the speed to 100 Mbps, even if the hardware supports 1 Gbps. This is especially true for integrated chip-based network adapters. Realtek.

How to update drivers:

• 🔧 Go to device Manager (Win + X → Device Manager).
• 🔧 Find the section Network adapters and select your card (for example, Realtek PCIe GbE Family Controller).
• 🔧 Right-click → Update driver → Automatic search.
• 🔧 If Windows does not find updates, download the driver from the manufacturer's website (for example, Realtek or Intel).

Also check your network card settings:

1. Open Control Panel → Network and Sharing Center → Change adapter settings.
2. Right click on Ethernet → Properties → Tune.
3. Tab Additionally: find parameters Speed & Duplex and install Auto Negotiation (auto-negotiation). If there is a fixed value (for example, 100 Mbps Full Duplex), change it.

Update drivers|Check Speed ​​& Duplex settings|Disable power saving in adapter properties|Test a different cable-->

5. Router CPU overload

If your router serves many devices at the same time (especially via Wi-Fi), it CPU may not be able to handle the load. As a result, cable clients receive lower priority and their speed decreases.

How does this manifest itself:

• 📉 The cable speed "jumps" or drops when actively using Wi-Fi.
• 📉 The router gets very hot (especially if it has passive cooling).
• 📉 The router's web interface is high CPU Load (processor load).

Solutions:

• 🔄 Restart your router (sometimes clearing the cache helps).
• 🔄 Disable unnecessary features: IPv6, UPnP, Guest network.
• 🔄 Limit the number of devices connected via Wi-Fi (especially smart gadgets that constantly exchange data).
• 🔄 If your router is older than 5 years, consider upgrading to modern models (for example, ASUS RT-AX86U or TP-Link Archer AX73) cope better with the load.

How to check the router's CPU load?

Most routers display CPU load in the web interface:

1. Go to your router's control panel.
2. Find the section System Monitor, Status or System Tools.
3. Look at the schedule CPU UsageIf it is constantly above 70%, the router is overloaded.

On some models (eg, MikroTik) for this you need to use Winbox or SSH.

6. IP addressing and MTU issues

Sometimes the speed drops due to incorrect settings IP or MTU (Maximum Transmission Unit). For example, if the router issues IP addresses to devices from different subnets or the MTU is set too high/low.

How to check:

1. Open Command Prompt (Win + R → cmd).
2. Enter

   ping -f -l 1472 ya.ru

   (replace ya.ru to any other site).
3. If a message appears Packet fragmentation required, MTU is too high.

The optimal MTU value for most networks is 1500If the test shows errors, try reducing the MTU to 1472 or 1400 in the router or network card settings.

Also check if there are any IP address conflicts:

• 🔍 In the command line, enter

  ipconfig /all

  (Windows) or

  ifconfig

  (macOS/Linux).
• 🔍 Make sure that IPv4 address devices and Main gateway are on the same subnet (for example, 192.168.1.x).
• 🔍 If the address starts with 169.254.x.x, then DHCP is not working - check your router settings.

7. External factors: interference and provider limitations

Sometimes the problem lies not in your equipment, but in external factors:

• 🌐 Provider restrictions: Some plans have separate limits for cable and Wi-Fi traffic (especially for office connections). Please check with support.
• 🌐 Electrical interference: If the cable runs near sources of electromagnetic interference (microwaves, refrigerators, powerful power supplies), the speed may drop.
• 🌐 DPI (Deep Packet Inspection): Some providers analyze traffic, which can slow down cable connections. Try using a VPN to test it out.

How to diagnose:

1. Connect the cable directly to the modem (bypassing the router) and check the speed. If it increases, the problem is with the router.
2. Call your provider and ask if there are any restrictions for LAN connections in your tariff.
3. Try the speed test on another device (eg. Smart TV or game console) via the same cable.

FAQ: Frequently Asked Questions

Can Wi-Fi be faster than Gigabit Ethernet?

Yes, but only theoretically. Modern standards Wi-Fi 6 (802.11ax) support speeds up to 9.6 Gbps, while Ethernet is limited to 1 Gbps (for most home networks). However, in practice, Wi-Fi rarely achieves even half of the advertised speed due to interference, distance, and the number of connected devices. If your Wi-Fi consistently shows 500–700 Mbps, while your cable only shows 100 Mbps, the problem is definitely not due to Ethernet limitations.

Why does cable speed drop at night?

This may be due to:

1. Overload of the provider's network (at night many people download large files).
2. Automatic updates on your devices (Windows, games, antiviruses).
3. Attacks on the router (If you have a weak Wi-Fi password, neighbors can connect and load the network).

Check if there are any background downloads running on your PC and temporarily disable Wi-Fi to make sure it's not the problem.

Which cable should I buy for maximum speed?

It's enough for a home network Cat 6 (up to 1 Gbps at 100 m). If you have a router or network card with ports 2.5G/5G, take it Cat 6a or Cat 7Please note:

• 🔹 Shielding: for rooms with interference, choose STP (shielded twisted pair).
• 🔹 Certification: There should be markings on the cable CM (for internal installation) or CMX (for external).
• 🔹 Manufacturer: Avoid no-name cables - they often do not live up to their stated specifications.

Will replacing the router help?

Yes, if:

• 🔄 Your current router is older than 5 years or has ports 100 Mbps.
• 🔄 You connect more than 10 devices simultaneously (especially via Wi-Fi).
• 🔄 The router gets hot and freezes under high load.

For a home network that prioritizes cable connections, choose models with:

• 🔹 Gigabit ports (10/100/1000 Mbps).
• 🔹 Support QoS with manual priority setting.
• 🔹 A powerful processor (for example, Broadcom BCM4908 or Qualcomm IPQ8072).

Examples of suitable routers: ASUS RT-AX88U, TP-Link Archer AX90, Keenetic Ultra II.

Is it possible to speed up a cable connection using software?

Yes, there are several ways:

1. Disable LSO (Large Send Offload): in the properties of the network card (Advanced → Large Send Offload v2) install Disabled.
2. Use alternative DNS: Sometimes the provider's default DNS services are slow. Try it. 1.1.1.1 (Cloudflare) or 8.8.8.8 (Google).
3. Set up Jumbo Frames: If your router and network card support it, install MTU = 9000 in the adapter settings.

Also check if there is a speed limit antivirus or firewall - temporarily disable them for testing.