PfSense and direct attached cable modem

  • Is it possible to directly connect my cable modem to the router? If configure the wan interface for dhcp it never gets an address or response from the modem… If I got it right the modem retrieves its ip from the ISP and the cable modem needs to get bridged to the wan interface... what am I missing here?

  • Connect everything together
    Try rebooting your cable modem first then reboot pfSense.

  • tried that before with no luck. So there is no special configuration needed for this setup? Simply setting the WAN interface to DHCP should do the trick?

  • Yes, that is all that should be required - what ISP are you with and what settings do they recommend for Windows?

  • i am with cablecom. My modem is currently connected to linksys WRT54GL router running OpenWRT. The MTU is set to 1500. What exactly do you mean by "what do they recommend for windows", the MTU?

    eth0.1    Link encap:Ethernet  HWaddr 00:18:F8:5F:xx:xx 
              inet  Bcast:  Mask:
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:35265875 errors:0 dropped:0 overruns:0 frame:0
              TX packets:17045557 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:0
              RX bytes:818423469 (780.5 MiB)  TX bytes:1751394547 (1.6 GiB)

  • If it works with OpenWRT, there's no reason it won't work with pfSense, assuming you use the same basic configuration.

    What you may have to do is have the OpenWRT host release the DHCP lease, power it down, plug in the pfSense host and then power it up.

    Alternatively, try cloning the MAC address of the OpenWRT host to the pfSense host.

    The question about "what they recommend for Windows" was about the general network config, if they recommended any non-default settings it would have pointed to a need to apply custom settings.  However, if you've got OpenWRT working, there's obviously nothing special needed.

  • Okay, I'll give that a try when I am back in front of the router hardware…
    But I have still some questions about this constellation: that means the cable modem acts on the ISP-side as a DHCP client and on the customer side as an DHCP server, is that correct? Is there no bridging taking place? Thanks for your help!

  • Unless you have a "all in one type" like this the cable modem is simply a bridge.

    Your ISP's DHCP server is on their premises.  They will hand your modem an IP but its for their use…

  • Well okay, so I assume its a simple bridge. But why do I need to configure the WAN interface for DHCP? The cable modem already got its ip and the WAN interface only needs to get bridged?  That means the router wan interface simple shouldnt care about anything ip-related stuff ???

  • Ah, you misunderstand - the cable modem is acting as a bridge between you and the ISP (while they share the same physical medium, the cable modem is usually on it's own logical network).

  • Okay, now I got it… The routers WAN interface retrieves its public IP directly from the ISP not from the cable modem... roger that :-) Thanks for your patience

  • Yep!

    Heres a good over detailed explanation in case your curious…    ;D

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