Cable Modem Assistance

  • Some information first:
    2.0-RC1 (i386) built on Mon Apr 11 15:52:08 EDT 2011.
    3x Intel Pro 10/100/1000 NIC.
    Standard (old) Intel motherboard and Celeron CPU.

    This is going to sound stupid but I need some assistance setting up a new cable modem with my existing pfSense setup. I have been using pfSense with an ADSL connection (modem set to full bridge, PPPoE) for some time now. I decided to add another internet connection which will provide superior quality bandwidth for general browsing. I am hoping to keep the ADSL which has more jitter and higher latency for general leech. This will lead on to some multi-WAN questions but I'll save those for later…

    The modem installer came over today and plugged everything in and I tested the connection on my noteboook, I was provided with an IP (static), subnet, gateway and DNS servers which I added manually to the Windows network config. Everything went well until I came to plug the modem into the pfSense box.

    I am stumped as to setting up and testing this cable connection. So far I have added a gateway called 'CABLE' with the settings:

    Gateway: <modem gateway="" ip="" from="" isp="">Alternative Monitor IP: <modem ip,="" assigned="" by="" isp="">(I assumed I would not be able to monitor their gateway...)
    I ignored the advanced options and added a description.

    Then I added an interface called 'CABLE' (super original, eh?) with the Type: Static (not sure if this is correct) and IP Address as my static IP (as assigned by ISP), assigned the gateway 'CABLE', blocked the bogon and private networks and clicked Save.

    All should have gone as planned but I'm not sure it has and am unsure how to test it. Ping from the 'CABLE' interface will sometimes have results and sometimes have 100% packet loss which I am sure is not the fault of the connection.

    Any advice or a guide I can look at? I have trawled the forums here but haven't hit on anything useful as yet. I am sure I cannot be the only one to ever have issues with this :C (my pride might suffer a mortal blow if that is true) so what am I doing wrong?

    TIA <3</modem></modem>

  • You'll have to power cycle your modem after switching devices.

  • Thanks for the heads up, I cycled the modem and took a look at the logs because the dashboard reported the interface as offline.

    I keep seeing this error pop up:

    kernel: arpresolve: can't allocate llinfo for <modem gateway="" ip="">/EDIT/

    I took a look at the logs before cycling the modem and saw this as well:

    What does this indicate? The subnet for my modem should be but I see no way to change that in either gateway or interface settings.</modem>

  • I seem able to use the cable modem to ping websites sucessfully via Diagnostics > Ping. I select 'Cable' as the interface and get results:

    Ping output:
    PING ( 56 data bytes
    64 bytes from icmp_seq=0 ttl=47 time=295.247 ms
    64 bytes from icmp_seq=1 ttl=47 time=295.041 ms
    64 bytes from icmp_seq=2 ttl=47 time=295.825 ms
    --- ping statistics ---
    3 packets transmitted, 3 packets received, 0.0% packet loss
    round-trip min/avg/max/stddev = 295.041/295.371/295.825/0.332 ms

    How am I able to actually test the connection with my browser? Simply make the gateway default in System > Routing? I seem to break things when I do that.

  • Your paying for a static IP?

    Some cable ISP's give this to you via dhcp…  Others you must code it in.

    My ISP makes me code it in. But I can still get an address via DHCP.

    Go to your wan page and set it for DHCP.   You should be able to go to your Status/Interface page and see if it worked...

    Also- what is the model of your cable modem?   Allot of them seem to be going the way of the cable gateway these days...  Thats a device that hands out a private LAN address to your stuff...   (

    Of coarse there is always      your pfsense address/wizard.php?xml=setup_wizard.xml

  • Can you see  ??

    Check your DNS settings…

  • The modem is a Motorola SURFBoard SB5101i, I've just started Googling for setups with that particular unit but can't see much so far.

    I'm not paying for a static IP so I've set the modem to DHCP and power cycled it. Is the DHCP typical for the majority of cable modems? To set this modem working on another PC or SOHO router equipment my ISP says that all I need to do is (for example connected directly to a Windows PC):

    -Set the IP to the one they gave me <public ip,="" 121.="" range="">-Set the subnet to
    -Set the gateway <also 121.="" range="">-Set the DNS servers.

    As far as I understand all of that should be able to be set inside pfSense. By looking at 'Interfaces > CABLE' all I can set is an alias IP (not sure what that does) and via 'System > Routing > CABLE' all I can set is a gateway IP and a monitor IP (again, not sure what that is) which aren't the same as the requirements above.

    All I need is a simple guide on how to do it. I already have a working ADSL connection, if possible I'd like to be able to test the cable connection alone to ensure browsing is stable then I'll move to look at load balancing.

    This is what 'Status > Interfaces' looks like at the moment. You can see it isn't picking up an IP from the modem.


  • I've just hooked the modem up to my PC and taken a look at the settings page at (thanks for the tip chpalmer) and it says that the DHCP server is enabled.


    The SURFboard cable modem can be used as a gateway to the Internet by a maximum of 32 users on a Local Area Network (LAN). When the Cable Modem is disconnected from the Internet, users on the LAN can be dynamically assigned IP Addresses by the Cable Modem DHCP Server. These addresses are assigned from an address pool which begins with and ends with Statically assigned IP addresses for other devices on the LAN should be chosen from outside of this range.

    What do I need to do to set this up in pfSense?


    Manufacturer website

  • @1080p:

    Then I added an interface called 'CABLE' (super original, eh?) with the Type: Static (not sure if this is correct) and IP Address as my static IP (as assigned by ISP), assigned the gateway 'CABLE', blocked the bogon and private networks and clicked Save.

    Can you uncheck the block bogons and private networks as a test?  Sometimes these Cable Company DHCP servers lie within a private address space.  Uncheck the blocks on the WAN tab, and hit Save then turn all network appliances off.  Start modem first and wait until it finishes its boot process, then start your pfSense box and pray for an IP.

  • Make sure you power down the cable modem each time you change the device plugged into it…

    They tend to grow attached to the mac address of the next device in line...  ;)

    You wont use the dhcp server on the modem. it does that to get your LAN up and running in case of a cable outage, assuming your LAN is all directly connected.  This modem does not appear to be a gateway device doing any routing for you, but just a bridge.

    What is the first number of the gateway they have assigned you?

  • Hi onhel, chpalmer

    My ISP DNS servers aren't in private address space. They are in the 203. range so blocking bogon & private should be fine right?

    When I connect the cable modem to my PC or a different piece of routing hardware I need to manually set my public IP address, the subnet, the gateway and the DNS servers. Is this not the same when connecting it to my pfSense box?

    I'm surprised I haven't seen a guide or similar for setting up a cable modem. They seem quite temperamental.

    So, if I were to begin over. What would the steps be for configuring the cable modem?

    ISP assigned IP: <121. range>
    Subnet: <>
    Gateway: <121. range>
    DNS: <203. range>

  • Upon further investigation I have learned that my cable modem does not actually hand out an IP address. I need to use the ones specified by my ISP. How does one go about setting that up with pfSense?

    Would I set the WAN connection as static?

  • I was given some advice in IRC with regards to my modem. I was making it a lot harder than it was.

    Instructions for TelstraClear users in New Zealand using pfSense 2.0:

    • During initial setup mark the connection as Static.
    • Enter the IP address written on your cable modem box or entered in your existing router setup. The subnet is usually which pfSense records using the CIDR notation (/24). If you have a different subnet configuration (unlikely) you can work it out here.
    • Enter the gateway IP address in the Gateway field (you can manage this later via 'System > Routing' in the WebConfigurator).
    • Enter DNS as desired (you can use any DNS provider you wish, they can be managed via 'System > General Setup' later on).
    • Profit!

  • Congrats!


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