How to Set the MTU to Auto in Comcast

By Mike Benson

Like most cable providers, Comcast uses an MTU size of 1500 bytes. Generally, the network devices provided by Comcast already have the optimal value of 1500 configured. However, some of their devices allow you to specify a manual or automatic configuration. In most cases, you should leave the MTU at the original value for optimal performance. If a circumstance arises requiring you to troubleshoot or change the MTU, you can change it to use automatic negotiation. This would let your device automatically detect and set your MTU value. This setting is found within their user interface, which is accessible using a Web browser.

Comcast Linksys Gateway WCG200Vx

Step 1

Open your Web browser.

Step 2

Enter “192.168.1.1” in the address bar and press “Enter.”

Step 3

Type “Comcast” in the “User name” field, and enter “1234” in the “Password” field. Click “OK” to log in.

Step 4

Click “Setup,” and then click “Basic Setup.”

Step 5

Click the “MTU” selection menu, and click “Auto.”

Step 6

Click the “Save Settings” button to apply.

Comcast Netgear Gateway CG814WG

Step 1

Open your Web browser.

Step 2

Enter “192.168.1.1” inside the address bar and press “Enter.”

Step 3

Type “Comcast” in the “User Name” box, and “1234” inside the “Password” field.

Step 4

Click the “Log In” button. This opens the Comcast gateway’s user interface.

Step 5

Click the “WAN Setup” link, which is found in the Advanced section on the left pane.

Step 6

Click in the “MTU Size” box located under the DMZ Address setting.

Step 7

Replace “1500” with “0” and click the “Apply” button to save.

Linksys WRT310N Gigabit Router

Step 1

Open a Web browser.

Step 2

Type “192.168.1.1” in your address bar and hit “Enter.”

Step 3

Log in to the WRT310N by leaving the “User name” field blank and entering “admin” in the “Password” field.

Step 4

Select the “Setup” tab, and then click the “Basic Setup” link.

Step 5

Expand the MTU drop-down menu, and click “Auto.”

Step 6

Click “Save Settings” to apply.

Tips & Warnings

  • The MTU configuration on the Comcast BEFCMUH4, SMC D3GNV and Arris TG852G gateway devices are always set to automatic and cannot be changed.