Comcast Business Static IP and your local area network (LAN)

Updated 2/25/2019 11:45:29 AM by Comcast Expert

Accessing the IP Gateway configuration

To gain access to the configuration pages of the IP Gateway (Comcast modem), enter (or the current LAN IP if the default LAN configuration has been changed) into the address bar of your web browser (e.g. Internet Explorer, Google Chrome, etc.) on a computer which has a connection to the internet through the Gateway. When the login page is displayed, enter the user ID: , and password: .

Setting Up the LAN

The LAN configuration tab of the IP Gateway contains the local (private) IP information distributed by the Gateway to your local network when DHCP (dynamic IP) is requested from it, or for devices manually configured with a local IP. These settings are only applicable to devices connected directly to the Gateway, either wirelessly or using an ethernet cable. If your network uses a different local IP addressing scheme, you can make those changes in the LAN configuration tab.

Keep in mind that these settings are only for devices that connect directly to the Comcast IP Gateway. For devices connected to a router before the IP Gateway, IP addresses are assigned and configured by that router.

IP Setup

The gateway is configured to use private IP addresses on the LAN side and to act as a DHCP server. The gateway's default LAN IP configuration is set to:

  • LAN IP address: (this will be the address entered into the default gateway field if manually configuring your LAN device)

  • Subnet mask: (this determines the number of available IP addresses)

  • DHCP range: (when manually configuring a LAN device, avoid using IPs in this range)

  • Domain suffix: (this is not typically required when configuring LAN devices)

If you have an existing TCP/IP network, you can change the Gateway's default LAN to integrate with it.

  1. Enter in the LAN IP Address: The LAN IP address is the IP address of the Gateway (a.k.a. the default gateway when configuring a LAN device) as seen by devices on the local network. The default LAN IP address of the Gateway is

  2. Enter the LAN Subnet Mask: The LAN subnet mask determines the quantity of IP addresses available for devices connected to the Gateway’s LAN to use. The default LAN subnet mask is allowing for 255 IP addresses to be used. When the LAN IP Address is set to and subnet set to, devices connected to the Gateway’s LAN can use any IP address between through, except for since that address is assigned to the Gateway.

  3. Enter the Domain Suffix: The default domain name is (not typically required in most network configurations)

  4. Enable LAN DHCP: (checked by default) Allows the LAN DHCP server to automatically allocate IP addresses to LAN devices. If this setting is not checked, all devices connected to the Gateway must be manually configured.

    • Select the Lease Time for the IP addresses assigned by the LAN DHCP server. A LAN client device that is assigned a LAN DHCP IP address is generally reassigned the same IP upon lease expiration. The default lease time is set to 1 Week.

    • Enter the DHCP Start IP. This will be the first LAN IP address of the range of IPs that can be assigned by the LAN DHCP server. The default start IP address is

    • Enter the DHCP End IP. This will be the last IP address of the range of addresses that can be assigned by the LAN DHCP server. All IP addresses between the Start and End IP will be available for the DHCP server to allocate to devices connect to the Gateway’s LAN. The default DHCP end IP is

  5. Assign DNS Manually: (unchecked by default) The domain name system (DNS) maps human-friendly names to computer-friendly numeric IP addresses. When unchecked, the Gateway will assign the default DNS server numbers currently in use on the Comcast network to your LAN devices. If Assign DNS Manually is checked, you can manually define the primary and secondary DNS servers that will be assigned to all PCs connected to the LAN via DHCP. If Assign DNS Manually is selected:

    • Enter the Primary DNS server that will be assigned to LAN devices.

    • Enter the Secondary DNS server that will be assigned to LAN devices.

  6. Select Apply.

Static Routing Setup

A routing table is the mechanism by which a modem or router memorizes where traffic should go when received. When a router is connected to the LAN of the Comcast Gateway, that router’s routing table is dynamically added (in most cases) to the routing table of the Comcast Gateway. This is done so that the Comcast Gateway knows where to send traffic destined for IPs which are on the separate subnet of IPs that are behind that router. By default, the Comcast Gateway’s LAN is set to assign IPs to LAN devices between and This is a subnet of LAN IPs. Most routers will assign IP addresses to their own LAN between and (a separate subnet). In order for internet traffic to reach a device on the subnet through the Comcast Gateway, that path must exist in the Gateway’s routing table. In some circumstances (not common), that route must be created manually. This is where static routes come in. If, for whatever reason, a router being connected between the Comcast Gateway and the rest of your LAN does not automatically update the Comcast Gateway’s routing table with its LAN information, use the Static Routing setup page on the Gateway to manually add that route.

A maximum of eight static routes may be added. To set up a static route rule, you must first know the destination IP address, the subnet mask of the destination IP address, and your LAN IP assigned to the router by the Comcast commercial gateway.

Create a static routing rule

  1. Enter a Name for the router that will make the route easier to remember (has no effect on the static routing function).

  2. Enter the Destination IP.

  3. Enter the Subnet Mask of the destination IP.

  4. Enter your local LAN Gateway IP address (The LAN IP assigned to the router connected to the Comcast commercial gateway).

  5. Select Add. The new static route will be added to the static routing table.

  6. Repeat steps 1 through 5 to add additional static routes.

  7. Select Apply to activate the static routes.

Remove a static routing setting

Select Remove on the static routing table to remove the route. The entire route is removed.

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