Just had Comcast Business Class internet installed (usage details at bottom of post). During the call to order I asked about the hardware they'd be providing and was told it was a docsis 3 modem that I'd have to pay $7.00/month for. Figuring I'd have to buy a router anyway, I decided to get my own modem - a Surfboard SB6121 Docsis 3.

I called in to tech support to ask some questions and learned that the modem they would have provided DID have a router built in. It's an SMCD3G-CCR. It's not wireless (we need wireless). The guy explained that it was better to have their hardware here because if there's a problem with our service and we're using our own hardware, chances are they'll blame it on our hardware and do nothing since they don't support it. He explained that I could still hang my own wireless router off their modem/router and if we ever had any service problems, we'd be able to plug directly into their hardware and they'd be able to tell where the problem is and they wouldn't be able to pawn it off onto "customer provided equipment".

That all said, a few questions: 1. Am I better off returning my Surfboard modem and getting the Comcast one?

  1. If I get a wireless router and plug into one of the ethernet ports of the Comcast device, should I NOT plug anything else into the Comcast device since it would be a different network from anything connecting via the wireless router? Is that correct?

  2. Given that I know VERY LITTLE about networking and setting up hardware like this... since I need wireless and will HAVE to get a wireless router to work with this Comcast device, do I need to do anything with the settings of the Comcast device? Do I use security on the Comcast device or the wireless router or both?

  3. Any suggestions or anything I need to think about, given this scenario, in order to use a business-type voip service like RingCentral or Jive or Nextiva?

  4. Any recommendations on a wireless router for this scenario?

We are running 2 PCs (possibly 3-4 in the future) - could be wired for the time being if needed but would prefer wireless; would like to have a networked hard drive and a networked printer; NEED business-type VOIP service asap for 2 phone lines. Would like to hook up some IP cameras at some point (but not the kind that require static IPs since I don't have one nor do I plan to pay Comcast another $15/month for one). I don't have or plan to have any type of web servers or anything like that. Want to use WPA or WPA2 security and take advantage of the NAT feature of the router for additional protection (that's the extent of my networking knowledge).

1 Answer 1


I had the previous model of the SMC cable modem that Comcast gives its business customers. I disliked it for the following reasons:

  • Doesn't support IPv6 (I recently checked the user manual of the new SMC, and it still doesn't support IPv6)
  • Can't be remotely rebooted
  • Only does 1:1 NAT and port forwarding, won't directly route static IPs
  • No wireless support, obviously

If you use the SURFboard, you'll merely have to stick a router behind it that's capable of routing your traffic in whatever manner you want.

If you don't have static IPs then it really doesn't matter much from a technical standpoint which modem you go with, today. But the lack of IPv6 support is going to hurt you in the future.

And, today, I have the SURFboard (and I'm still on Comcast). It does support IPv6, stays completely out of the way of routing and lets me do whatever I want with my internal network.

BTW, NAT doesn't protect you from anything; the firewall does. NAT just causes all sorts of trouble, which is why IPv6.

Either way you're going to end up with two boxes.

(And I'm not really going to touch the office network design aspects here, since they really are separate questions and should be treated separately...)

  • 1
    Juniper SRX210/220/240 models have DOCSIS3.0 modules available :) Nov 6, 2012 at 23:41
  • NOW you tell me. Nov 6, 2012 at 23:46
  • I have used three different SMC models provided by Comcast and none of them supported bridge mode. And all of them would be remotely reset by Comcast technicians any time someone called about anything, thereby wiping out any NAT mapping I had set up. I ended up buying my own modem and router. And strangely enough, never had to call Comcast again because all the weird connectivity issues we had went away! (YMMV)
    – longneck
    Nov 6, 2012 at 23:58
  • Great info and anecdotes. Thank you. My Surfboard modem does support the IPv6 which based on your comments is good. I'm in the process of setting up an old standby WRT54G router I had laying around as a stopgap until I decide what router I really want. My understanding of NAT is that it provides "protection" by "hiding" what's behind it from the evil outside world's prying eyes - I do understand it's not the same as a firewall but it's better than just connecting my PC to the modem direct. Does this modem or router HAVE a firewall I don't know about?
    – Buck
    Nov 7, 2012 at 1:07
  • @Buck NAT just gives you a firewall by default. Virtually any home/SOHO class router will do this. For a longer discussion, you might wish to read Switch to IPv6 and get rid of NAT? Are you kidding? Nov 7, 2012 at 1:14

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