Setup Guide: Routers that are not able to turn off DHCP Service (Legacy)

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    Martins

    Today I have my Xfinity Gateway replaced because it was faulty, and for some reason this "tricky" no long works by

    change both Beginning Address and Ending Address to Firewalla's IP Address... It says that the Beginning  and Ending Address cannot be the same !

    I think they send me with new firmware, because the gateway looks like the same as the old one!

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    Firewalla

    What is the model of the xfinity gateway?

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    Martins

    Hi there, follow the information about the gateway:

    Gateway: Xfinity XB3

    Model:DPC3941T
    Vendor:Cisco
    Hardware Revision:1.0
    Processor Speed:2400.01 MHz
    DRAM Total Memory:1024 MB
    DRAM Used Memory:990 MB
    DRAM Available Memory:33 MB
    Flash Total Memory:4 MB
    Flash Used Memory:3 MB
    Flash Available Memory:1 MB
     
    System Software Version:
    eMTA & DOCSIS Software Version:2.3.10.13_5.5.0.5
    Software Image Name:DPC3941_3.12p8s1_PROD_sey
    Advanced Services:DPC3941T
    Packet Cable:2.0
     
     

     

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    Firewalla

    The DPC3941T should fully compatible with Simple mode.  Are you having problems with it?

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    Martins

    I'm running it with simple mode with no problem !

    But if you desire to run it in DHCP mode, probably due a gateway firmware update it doesn't allow you to do this trick by set the IP range the same start and end.

    My old gateway (same model) I was able to do this! 

    Thanks!

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    Peter Shaffer

    Correct. This no longer works on the XB6 as well.

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    Firewalla

    @peter, any details on why it is not working on the XB6?

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    Peter Shaffer

    Same reason as posted above. No longer able to set the IP range to the same start and end. Work around may be putting device in bridge mode and using a supported router.

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    Firewalla

    Peter, interesting.  So the new firmware forcing at least 2 devices in DHCP? if that's the case, the method may also work (one device may not be able to be monitored).  

    Also, if you can, please try the "experimental simple mode" (you will need to turn on DHCP on your router first).  Experimental simple mode is a set of customized fixes, that may make the router work. 

     

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    Martins

    Hi Firewalla team, so by set DHCP Beginning Address: 10.0.0.237, DHCP Ending Address: 10.0.0.238... on XB6 and assign the 10.0.0.238 to a fake device will work on IPV4 !

    What about the IPV6 that XB6 will not allow to disable it ?

    Any solution for this case ? I can perform any test with my XB6 if needed, just let me know how to proceed!

    Thank you !

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    Joe Avery (HakAtIt)

    I attempted to install with a XB3 in DHCP mode. I'm able to connect to the device, configure it. I then reserved the address  (10.0.0.10) , and reserved a Fake one (10.0.0.11). Everything still working ok. Some devices already getting a 192 address from the Firewalla. I then set the DHCP range to just the two devices. At this point I loose internet connection from the devices with 192 addresses and I'm unable to connect to the Firewalla from the phone on cellular. I opened the DHCP pool again, 10.0.0.5-150, and it starts working. 

    Any thoughts on this, ideas on what I should try? 

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    Firewalla

    @joe can you send an email to help@firewalla.com so we can help you take a look at the problem?   

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    Joe Avery (HakAtIt)

    Update on what I found. Working with the tg1682g, When I'd reduce the DHCP pool to less than 15 devices, the unit would stop forwarding/ routing DNS queries. I was able to ping from my laptop, and the Modem could resolve from the test page, however no device inside the network could resolve a DNS, if the DHCP pool was less than 15 devices. I tried it using DHCP range of 10.0.0.10 to 10.0.0.25 and 10.0.0.210 to 10.0.0.225, with the same results. The only device I had connected was my laptop, wired, with WiFi on the modem off.


    I ended up simply reserving 14 addresses, and using the Firewalla in DHCP mode. Unfortunately there continued to be issues with the Firewalla dropping out, or not giving out addresses very consistently. Most importantly the Comcast modem would give out IPv6 addresses and the devices would just work and ignore the DNS from the Firewalla (open DNS) being used to additionally prevent porn and other unsafe searches. Hopefully the Firewalla gets IPv6 support soon.

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    Ray Hamel

    So I have this modem https://www.rogers.com/customer/support/article/learn-more-about-the-rogers-ignite-modem

    Will the Firewalla Blue work?  I don't think I can disable DHCP on it., but I can edit the LAN start and end ranges for DHCP.

    Do you think this would still work?  I think this is the model info for it:

    Technicolor CGM4140COM
    Rev 2.2

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