pfsense router and comcast setup

Posted on 2012-03-12
Last Modified: 2013-02-17
   I have a comcast business WAN connection.  I've also requested a block of CIDR/28 addresses.  The internal side of the cable router utilizes this address space.  I'm unable to physically bridge the cable router, and I can't figure out how to use the CIDR/28 addresses in a DMZ subnet on the inside of my pfsense router...the pfsense router is connected to the cable router using one of the CIDR/28 addresses.  What's the best way to set this up so that the DMZ on the inside of the pfsense router can utilize the CIDR addresses, while still providing packet filtering/NATing?  How would I go about setting up the gateways?

Thanks in advance for your advice.
Question by:Heraldstorm
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LVL 44

Expert Comment

ID: 37713130
What is the brand and model of the comcast modem?

Author Comment

ID: 37713142
Sorry, it's an SMC 8014
LVL 44

Expert Comment

ID: 37714952
A /28 should give you 14 IPs... and typically, the ISP will give you 13 of them and keep one to use as your Gateway IP, which would really be a port on their layer 3 managed switch.

1 of those 13 IPs will be assigned to the WAN port of the SMC (that's the Gateway to your /28 from Comcast's end); that leaves you 12 IPs. All 12 of those should be covered by a static route that sends traffic back and forth to the Gateway address at Comcast, and the route on their end sends all traffic bound for your /28 range to the IP address assigned to your SMC's WAN port.
If their instructions aren't clear how to do that, you should be able to call their Biz support, and they should be able to configure the SMC remotely for you. That should be included in the Biz service (i.e. it should not cost anything extra for them to do that).

If you want to use another router to do NAT to a private range on your LAN, give its WAN port one of those 12 IPs and connect it to the SMC (you'll need a couple/few simple dumb switches to break out enough ports for all 12 IPs from the 4 ports on the SMC). I don't see why you would need to use any DMZ at all, though.

Check out this message -
To see that whole thread, click the " [Connectivity] Attn: Former Insight sticky IP customers" part of the 'bread crumb trail' at the top.
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LVL 44

Expert Comment

ID: 37715066
Oh... and if they didn't give you ANY instructions on how to set it up, you need to disable the SMC's DHCP server and firewall.
I find conflicting info to disable the firewall... online someone  said to
check the box next to Disable Firewall for True Static IP Subnet Only in its Firewall settings.
But in its manual it says to just UNcheck the Enable Firewall Module box.

Enable/Disable SMC8014 Firewall

Author Comment

ID: 37715887
Thanks, I appreciate the time you took explaining all that.  I'm pretty good up to that point.  My problem is that I have internet facing servers and I have private servers and workstations.  The whole reason I'm running my own router is to gain added security benefits.  I can't run spam filtering and antivirus detection on the SMC router, so I'm installing my own that will.  My problem is that I want to be able to protect and limit the traffic to my internet facing systems.  Typically, this is done in a DMZ.  Due to the limitations of the SMC and the necessities of its configuration, I can't have the DMZ in between the two different routers and still get the kind of protection I want.  Thus, I want to bring the DMZ behind my internal router (running pfsense), but I'd really rather not have to set up 1:1 NAT.  I can set up a bridge, but I'm not sure if it's a good idea bridging an internal interface with a WAN interface.  I might be able to set up some static routes, but I'd need some hand holding to do that.

That's primarily what I'm looking for help on at this point.

Author Comment

ID: 37716146
It might help if I supply a diagram...
net diagram

Accepted Solution

Heraldstorm earned 0 total points
ID: 37717234
OK I had to go buy a book to get the answer, but essentially, I have to bridge my internal DMZ interface to the WAN interface.  This will prevent any direct connections to systems on other interfaces on the pfSense firewall, because the DMZ interface and the WAN interface are both using the comcast router as the default gateway, and the comcast router doesn't know anything about the other interfaces or networks hosted on the pfsense box.  To get around this, I can (possibly, maybe, haven't tested yet) use OpenVPN to get inside one of the private LANs or I can use the CARP feature of pfSense and set up some virtual IP addresses in the DMZ (this would take up one of the public IPs) and after setting up a 1:1 NAT, the pfSense router would be able to route that traffic back into one of the private LANs.

It's not optimal, but it's workable.  It's certainly the best I can expect off of a Comcast router.  They design their systems for their control, not the end user's...good or bad.

Anyway, thanks to Darr247 for the input.  Glad I finally resolved this!

Author Closing Comment

ID: 37734439
I found the vendor recommended way to do exactly what I'm trying to do.

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