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Bridge Mode vs Static IP with Cisco DPC3939B

Stfarris
Visitor

Bridge Mode vs Static IP with Cisco DPC3939B

Hello

 

I am trying to set up a VPN, and need to get the public IP address to my VPN router.  I have the Cisco DPC3939B business modem.  It appears there are two ways to accomplish my goal, and I am interested in the differences.

 

First, I could have the modem put in "Bridge Mode".  Then it will simply pass the IP address to whatever is connected to the LAN ports on the modem (if I understand correctly).

 

Second, I could get a static IP address and have that address passed through to the VPN router.  What I am unclear of is how to pass the IP address.  Does Comcast set this up?

 

I have tried simply port forwarding, but the router doesn't truely see the public IP address and instead sees it's address as the private IP address served by the modem.

 

Thanks for any words of wisdom.

 

steve

7 REPLIES
Tom1
Visitor

Re: Bridge Mode vs Static IP with Cisco DPC3939B

Did you get any information on doing this?  I'm trying to determine the current wisdom on this issue.

 

Thanks.

 

Tom

Stfarris
Visitor

Re: Bridge Mode vs Static IP with Cisco DPC3939B

Not a peep.  I followed the instructions for emailing a specific person and didn't get a response either.  So I"m not much help.  Let me know if you get anything working.

 

steve

Official Employee

Re: Bridge Mode vs Static IP with Cisco DPC3939B

Hi Stfarris and Tom1.

 

I can help with your questions.

 

You are able to use bridge mode with the DPC3939B. However, this would stop all routing functions including WiFi, port forwarding and firewall functions making the device a stand-alone modem. This will also disable all ports except for 1 to use with a singular device. 

 

If you do decide to get a static IP, the static is unfiltered so it wouldn't be passed on to a device. The static would need to be assigned manually to your device on your side. 

 

Please do private message me if you do need any additional assistance.

Stfarris
Visitor

Re: Bridge Mode vs Static IP with Cisco DPC3939B

Hello Comcast Phil, 

 

Thanks for responding.  I have a couple questions, and I thought I would ask them here since the answers might be useful to others.

 

1)  In the modem configuration, there is a setting for "bridge mode".  How is that different from what you would do, and am I able to configure that on my own?  Once in bridge mode, do I completely lose access to the modem configuration?

 

2)  I understand that bridge mode will disable all the routing features of the modem.  You say only one port on the LAN side would be active.  Which port?

 

3)  If I stay with a dynamic IP from Comcast, will I still get a DHCP server when my internal router attempts to connect?  Or do I need to somehow figure out what the IP address is to input that to my router?

 

Steve

Official Employee

Re: Bridge Mode vs Static IP with Cisco DPC3939B

Hi Stfarris.

 

I can certainly help with your inquiries regarding your gateway.

 

1) That setting for "Bridge Mode" that you see in the gateway is the exact same thing we set up. We just enable it so there's no difference in the Cisco DPC3939 if we do it or if you do. Once in bridge mode, you still have access to the gateway's graphic user interface. 

 

2) Port 1 is the only one that should be LAN active in bridge mode.

 

3) Either option is possible. The DHCP can assign this or you can set up the equipment for a specific address. However, this really depends on your network's needs. You'll need to review which option is better suited for you as this would be past our demarcation. 

 

Please let me know if you need anything.

Stfarris
Visitor

Re: Bridge Mode vs Static IP with Cisco DPC3939B

Hi Phil

 

Perfect, you have answered my questions.  It sounds like I can put it in bridge mode myself to test.  Based upon your response, if it doesn't work out I can put it back to "normal" mode myself.  Once it is passing the IP address through to my internal router, would I use that IP address to access the modem?  Or would I need to connect on USB?

 

steve

Official Employee

Re: Bridge Mode vs Static IP with Cisco DPC3939B

Correct. The DHCP IP that is requested by the gateway will be used for your device not to be confused with the other IP address of 10.1.10.1. 

 

https://business.comcast.com/help-and-support/internet/setup-manage-comcast-wifi-business-wireless-g...

 

Please do let me know if you need anything.

 

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