How to set up IP Passthrough for Cisco 3848V modem

Document created by shaw-jody on Jul 27, 2017Last modified by shaw-jody on Aug 1, 2017
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Whether you're looking to use a third party router or troubleshoot possible connectivity issues, IP Passthrough allows you to assign a public IP address to a device connected to your Cisco modem, effectively bypassing the Cisco's internal router. Follow these instructions to set up the IP Passthrough feature on a Cisco DPC3848V Docsis 3.0 modem.

 

To use IP Passthrough, you'll need to ensure that you have a second dynamic IP address available for your modem. The automatic availability of multiple dynamic addresses is dependant upon your Internet service package. Once you have enabled IP Passthrough, the device that receives the public IP address will no longer be able to access the Cisco's user interface (as described below). Please contact customer support to confirm or arrange for your free IP address: Shaw.ca/ContactUS. Once you have confirmed the availability of a second IP address, please follow the setup steps outlined below.

 

This article provides insight into:

What is IP Passthrough?

Setup instructions

Verification

Important notes

Did You Know 

 

Once IP Passthrough is enabled for a connected device, that device will no longer be able to access the Cisco GUI (default 192.168.0.1) as it is operating outside of the Cisco's DHCP service. Only the defined device will receive a public IP address, all other devices connected to the Cisco (via Ethernet or WiFi) will receive internal IP addresses (i.e., 192.168.0.X).

                               
What is IP Passthrough

IP Passthrough allows you to assign a public IP address to a device connected to your Cisco modem, effectively bypassing the Cisco's internal router. IP Passthrough means the Shaw supported device terminates the cable, authenticates with the network (Receives a WAN /Public IP) and shares that IP address with single specific device connected to the Shaw supported equipment.


In other words, while in IP Passthrough mode, the configured specific MAC interfaces does not use the routing code at all (except for some special cases) when handling received IP packets. Packets received for the cable interface are delivered directly to the defined interface. Similarly, packets received for the particular interface (everything except broadcasts/multicasts) are sent to the cable interface.

This configuration is often times suitable for:

  •  a business customer desiring to connect third party equipment to supported Shaw equipment
  • for “Advance” users with specific needs of Public IP on specific devices.

Note 

 

The IP Passthrough configuration activates similar to “Bridge” mode functionality on supported equipment but this time only for specific devices, which could be connected by Wireless for example. Similar functionality isn’t possible in pure Bridge mode.).

                 

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Setup instructions
Follow these instructions to set up IP Passthrough for your Cisco modem. 

 

  1. Log into the Gateway IP (default: 192.168.0.1)
  2. Enter username and password
    • Default User: cusadmin
    • Default Password: Serial Number of the Modem
  3. Click on Applications & Gaming tab
  4. Click on IP Pass-through tab

 

IP Passthrough Cisco Interface

 

 

IP Passthrough set by MAC Address

 

IP Passthrough on Cisco DPC3848V can only be set by MAC Address. This allows you to specify the mac address of the specific device on your local network that should receive the public IP (generally a router connected via an Ethernet cable). You will need to specify MAC address of the relevant device network interface, which can be hooked up to any Ethernet port or by Wireless connection.

 

  1. Check the Enabled check box
  2. Enter the MAC address of your network interface, which user desires to relate with Public IP
  3. Click on Add
    Cisco IP Passthrough checkbox enabled

  4. Verify the Mac address appears in the list box below
  5. Click on Save Settings
    Cisco IP Pass-through Saved Settings

  6. You will be presented the next pop up window, after Save Settings was clicked. Once the popup window disappears

 

Cisco IP Passthrough Settings being Saved

 

Cisco IP Passthrough Saved Settings

Related: IP Passthrough for Arris SBG6782, IP Passthrough Hitron CGNM-2250

 

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Verification

To verify that IP Passthrough is functioning, you need to check if current device with relevant MAC interface received a public IP, which means IP Passthrough feature is functioning. This can be verified in the Network Connection Status Properties.

 

IP Passthrough Verification

 

If the network interface status in the OS doesn't update (still shows as 192.168.0.1) then the status needs to be refreshed. The options to do so are:

  • Renew the IP status by disabling and enabling the network interface OR
  • Disconnect and connect again the Ethernet Cable or Wireless Connection OR
  • Restart the modem:
    • by powercycling OR
    • On the Gateway page (192.168.0.1), login, go to the Administration tab, Device Reset sub-tab.It will prompt for the password. Once entered, click on Device Reset operation.

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Important notes

To view the MAC address of your interface, take the following steps (Window 7 example):

  1. Go in to Network Connection
  2. Double Click on the relevant Network Interface
  3. Click on Details within connection Status.
  4. Physical Address will display the MAC address of the interface.

 

IP Passthrough > Network Connection Details

 

  • Only defined devices will receive a Public IP. All other devices connected to the Cisco DPC3848V will continue to receive local IP.
  • Shaw doesn't suggest using this feature unless you are an "Advanced" or Business user with  actual need for such functionality.

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