How do I configure a CradlePoint CBA750 in IP pass-through mode?

Installation summary: This document is intended to assist field engineers for configuring a CradlePoint CBA750 in IP pass-through mode to provide the carrier’s IP address to another router or computer.

1.  If possible, make sure prior to installation that your modem or SIM card has been provisioned with your carrier and that the correct APN has been assigned for your region. 

A. If your carrier has provided you with a static IP address, make sure to copy down the IP address and region APN.
B. If you are using a dynamic Ip address, you will use the default such as “vzwinternet (VZW), broadband (AT&T), Sprintpcs.com (Sprint Realm) and Clearwire-wmx.net (Clear Realm).
C. Place the modem in its final resting place before proceeding.
D. Test your modem to confirm it has been provisioned by plugging it directly into your laptop. Using “IPCONFIG/ALL” confirm your IP address? Can you pass traffic across the cellular WAN?
     2.  Ensure that the CBA750’s IP pass-through switch is set to O (NAT/configuration mode) instead of | (IP pass-through mode).


     3.  If External Modem, plug the cellular modem into the CBA750’s USB1 port, connect the AC power adapter and attach an Ethernet cable to a laptop or desktop computer.

4.  If a Modem CAP solution is being used, follow the instructions that are included.

5.  The CBA750 will attempt to connect using a modem.  This process may take up to fifteen minutes.  When the CBA750’s USB1 LED turns solid green, this indicates that the modem has connected.

  • If the USB1 LED remains flashing after fifteen minutes, you should verify with your carrier whether the SIM card (or modem) has been provisioned before calling CradlePoint technical support for assistance.

     6.  From the computer attached to the CradlePoint, use a web browser (we recommend Google Chrome or Mozilla Firefox) to navigate to the CradlePoint’s administration UI at http://192.168.0.1.
7.  Log in using the administrator password (by default the last six characters of the MAC address from the label on the bottom of the router).
8.  Check the modem’s signal strength by going to MODEM and then INFO

  • Make note of the “Service Display,” “Signal Strength (dBm),” “SINR,” “CINR” and “EC/IO” (not all of these will be available for all modems).  The “Service Display” indicates which 3G or 4G technology you are connected at.  For example, an LTE 4G modem should show “Service Display:  LTE” when connecting in a 4G area.

     9.  Acceptable values for these options are as follows:

Signal Strength (dBm):          -85dBm or better           (-40dBm is better than -90dBm)

SINR:                                       7 or greater

CINR:                                       9 or greater

EC/IO:                                    -10 or better                  (-1 is better than -10)


*NOTE: Signal strength and signal noise should always be looked at collectivity. A good signal with bad noise could yield poor connectivity.

10.  If any of your signal values do not meet the above requirements, you will need to physically move the modem to a location that receives a better cellular signal, add external antennas, or replace the USB modem with a CradlePoint modem cap that can receive a better signal.  If your signal values are acceptable, proceed to step 11. Remember the CBA750 has a power over Ethernet port that can be used with any

11.  Verify the Internet connection is working by going to TOOLS and SYSTEM CHECK, and then using the PING TEST box to verify that you are getting ping responses from google.com and 8.8.8.8 (Google’s public DNS server).  If you are connected to the Internet, proceed to step 15.  Otherwise, follow steps 10, 11, & 12 for assistance getting the modem connected.

12.  If using a 4G LTE modem in a 3G-only area, follow these directions to force the modem to connect at 3G or less.

13.  If using a 4G WiMAX modem in a 3G-only area, follow these directions to force the modem to connect at 3G or less.

14.  If your carrier requires you to input an Access Point Name (APN), follow these directions.

15.  Verify the CBA750’s WAN IP address from STATUS -> WAN locate the IP Address.  This is the IP address that will be passed-through to the connected device.

  • If this IP does not match the static IP assigned by your carrier, contact them for assistance before proceeding.

    16.  If you are using a static IP address, follow the below directions to configure the CBA750.  This setting is not needed for dynamic IP addresses.

  1. In the CBA750’s web UI, go to BASIC -> IP PASSTHRU
  2. For the IP Passthru Subnet Mode, place a dot next to “Custom subnet mask and gateway
  3. For the “Subnet Mask,” enter “255.255.255.0″
  4. For the “Gateway Address,” enter X.X.X.1 where X.X.X are the first three octets of your static IP address.
  5. Click Save Settings and then Reboot Now when prompted.
  6. Flip the CBA750’s IP pass-through switch from the circle “O” to the line “|.”  The CradlePoint will reset itself.  Your computer should obtain a new IP address from the CradlePoint.  Verify that your computer is now receiving the same static IP address that the CBA750 showed earlier on the STATUS -> WAN page.  Verify that you still have Internet connectivity.

    17.  The CradlePoint CBA750 has now been configured for IP pass-through mode and will pass through the cellular carrier’s IP address to the device connected to its Ethernet port.

  • After making these changes, the CBA750 will act as a transparent bridge to allow the device connected behind it (such as a Cisco or Juniper router) to obtain the carrier’s IP address via DHCP, or by manually specifying the carrier’s IP address with a 255.255.255.0 subnet mask and an X.X.X.1 default gateway IP address (where X.X.X are the first three octets of your static IP).  Remember that the CBA750 must be rebooted any time that you change the device connected to its Ethernet port.  Also be aware that many LTE carriers use low MTU frame sizes (commonly 1428 MTU) and will immediately drop the LTE connection if enough fragmented packets are sent within a short period. It is recommended that an MTU of 1350 be used on the customer’s device (Cisco, Adran, Juniper, Fortigate) and an MTU size of 1400 be set on the Cradlepoint.  


Wipipe Managed Services

  1. If the device is managed by Wipipe, check with your system manager to confirm the credentials for the customer account and verify that the device reports into Wipipe. It will need to be implemented into the proper group or into the “unassigned” group.
  2. If this is a large rollout, request the MAC addresses from Operations and import into Wipipe per the customer’s instructions.

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