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Thread: How to setup a Comcast SMC cable modem/router -- no static IP's

  1. #1
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    How to setup a Comcast SMC cable modem/router -- no static IP's

    This post is a summary of some difficulties I worked through to set up Comcast's SMC four port modem/router device for a small business network -- with no static IP's. Hopefully, if there are better, more secure adaptations, more knowledgeable people will chime in, but, if you face setting up CC's SMC device for your network and you're not an expert or even well-versed in networking (my case), the following account may be helpful to you.

    Previously, we had the cat5 wire from the Frontier DLS modem connected to the Internet port of a Netgear FSV318v3 Prosafe router and that 8-port unit connected to 7 PC's and a LAN port of another 8-port switch. The remaining seven ports on the switch fed more devices. The Netgear LAN was set up on the 192.168.0.1... addressing scheme and we had specified or reserved IP addresses for a printer, the timeclock and security camera system, haphazardly choosing 100, 4, and 11 as the fourth set of digits for these three devices' addresses, as they came into the system. With the Netgear unit, we could and did reserve the IP addresses related to the MAC addresses of these different devices.

    On the day of the Frontier DSL to Comcast cable triple-play switch-over, basically, on the Internet side, the SMC modem replaced the DSL modem and after a few minor tweaks by the installer to shut off DHCP in the SMC (leaving DHCP still to be served by the Netgear), all our network was running, even faster than before. The Netgear continued to shut Internet access off on the graveyard shift by scheduled rules.

    After the dust settled and the phone lines and everything else was settled in, running speed test on the workstations gave results of 8-9 Mbps download and 2-3 Mbps upload, which was well below the 22/5 expected. Speed test's on a port of the SMC unit ran a smooth 30+/ 6.5 Mbps dn/up. An initial call to CC tech support resulted in the tech doing something from their side which I understood was putting the SMC unit in "bridge" or "pass-thru" mode which made the device interface inaccessible to us via the 10.0.10.0 address link. Speed may have improved just slightly, but not above 9.5 Mbps -- still very slow speed.. Some research on the web indicated that our Netgear units (or, the way I might have had them mis-configured) was the likely cause of the slow-down.

    Presently, after one harrowing afternoon of quite unproductive calls with Comcast tech support, and thankfully avoiding the pitch that we needed to purchase static IP's to get our network printer and other two devices working while staying with the SMC's 10.0.10.0 default addressing scheme, what we have now, getting the wonderful 30+/8 Mbps dn/up speeds, is the cat5 cable from the SMC modem, plus all our cat5 lines from our other ~12-14 devices now plug into a Netgear JFS524 ProSafe 24-port 10/100 Fast Ethernet Switch. ($85 purchased from Amazon in preparation for the change-over.) This switch is rated to convey 200 Mbps to each port and our system continues, now, to run on the 192.168.0.1... IP addressing scheme, such that our three network devices which need an assigned, consistent IP address still have them.

    Once the wiring is set and the network (except for network printing, etc.) are running on the SMC's 10.0.10.0 scheme, how does a networking novice get the system to actually WORK??


    It turns out this is very simple. And, it turns out that one certainly does not need to buy a bank of static IP addresses from Comcast as they suggested to get network printing, a time clock or security camera back in operation.

    What we did, which should have been during slack times on the network was, from the browser, access the interface of the SMC modem/router/four-port switch via its default 10.1.10.1 IP address. And then log in with the username and password.

    In the LAN Setup Section:

    1. Set the IP Address: 192.168.0.1 (was 10.1.10.1)
    2. Set DHCP start: 192.168.0.101
    3. Set DHCP end: 192.168.0.199
    This leaves 101 - 199 to be dynamically assigned to workstations as they join the network but leaves 192.168.0.2 to .100 outside of DHCP space and thus available for assigned IP addresses like, in our case, 192.168.0.4 or 192.168.0.11 or 192.168.0.100 which had already been assigned previously in hardware setups and/or specified as ports to print to, and/or for software to read from or write to.
    4. Save these changes in the SMC setup -- which disrupts all LAN connections (devices were on 10.1.10.1...)
    5. Reset the dynamically assigned IP's of workstations and devices by re-booting or, at Windows
    workstations --> Start/Run/cmd to get to a DOS prompt and then
    type: ipconfig /release <Enter>
    and then: ipconfig /renew <Enter>

    If all is well, network printing will resume, the timeclock and security cameras and what-not will all continue to work as before, and when you run speedtest.comcast.net you'll at least get 22 Mbps download and 5 Mbps upload, or maybe even better!

    In my recent learning episode on "how to setup a Comcast SMC cable modem/router", I was very, very fortunate to have gotten some last-minute onsite help from a very capable young man named Craig who currently provides tech support for and through Copiers Plus in Lafayette, Indiana. Thanks, Craig. You are the man!

    Good luck!

    Ralph
    http//:www.frostscientific.com

  2. #2
    Moderator YeOldeStonecat's Avatar
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    There's a lot of confusion going on in that post...especially when it comes to "static IPs".

    First...there are 2 sides to your network when it comes to routers that run in gateway mode. Static IPs can refer to either side...it depends on what you're talking about.
    A static IP...or a block of static IPs, that you purchase from your ISP....are the "public" IP addresses that you obtain from your ISP. This is the IP address that you see when you go to "www.whatismyip.com". This is typically only done on business accounts from the ISP, and typically only used when you have things like a mail server running on your network (so your MX record points to it), or a VPN server, or remote access services like Terminal Server/TSGateway/RemoteWebWorkplace...stuff like that.

    Now...static IPs on the inside...on your private network...such as when you have servers, network printers, network scanners/MFPs, stuff like that...Comcast (or whoever your ISP is) doesn't care about those...nor should they. Those are YOUR static devices which are on your private class C network behind the router (like 10.1.10.xxx behind the SMC or 192.168.0.xxx or 192.168.1.xxx behind your Nutgear or Stinksys router)....the ISP doesn't care about those, they have no need to. It's behind NAT..the basic hardware firewall of your network.

    Now lots of us setup networks for our clients on Comcast business setups....typically with the SMC gateway. We want to use our own routers for various purposes, and not the SMC gateway. This is very easily done. The proper method is to take the sheet of paper that Comcast gave you, for your static IP block. Take the first usable static IP address...and assign that statically to the WAN port of your own router....and you'll see the default gateway for that IP is 1x number higher or lower...enter that for the gateway, enter your own DNS or Comcasts DNS...and uplink your own routers WAN port to one of the LAN ports of the SMC gateway. You can leave DHCP enabled on the SMC...your router is assigned with a static external interface, and your entire network will plug in BEHIND your own router. So DHCP from the SMC will not impact your own network. What you want to do is log into the SMCs web admin, firewall section, and put a check in the box for "disable firewall for true static IP subnet". Now your own router is not double NAT'd. Your entire network is behind it....192.168.0.xxx, there's just 1 gateway..and your own routers WAN interface is on the proper static public IP address from Comcast.

    And yes the Netgear ProSafe routers will typically be a bottleneck on todays faster Docsis 3 networks....even older Docsis 2 networks of higher speeds. The ProSafes are not very fast.
    MORNING WOOD Lumber Company
    Guinness for Strength!!!

  3. #3
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    Quote Originally Posted by YeOldeStonecat View Post
    There's a lot of confusion going on in that post...especially when it comes to "static IPs".

    First...there are 2 sides to your network when it comes to routers that run in gateway mode. Static IPs can refer to either side...it depends on what you're talking about.
    A static IP...or a block of static IPs, that you purchase from your ISP....are the "public" IP addresses that you obtain from your ISP. This is the IP address that you see when you go to "www.whatismyip.com". This is typically only done on business accounts from the ISP, and typically only used when you have things like a mail server running on your network (so your MX record points to it), or a VPN server, or remote access services like Terminal Server/TSGateway/RemoteWebWorkplace...stuff like that.

    Now...static IPs on the inside...on your private network...such as when you have servers, network printers, network scanners/MFPs, stuff like that...Comcast (or whoever your ISP is) doesn't care about those...nor should they. Those are YOUR static devices which are on your private class C network behind the router (like 10.1.10.xxx behind the SMC or 192.168.0.xxx or 192.168.1.xxx behind your Nutgear or Stinksys router)....the ISP doesn't care about those, they have no need to. It's behind NAT..the basic hardware firewall of your network.
    I appreciate you clarifying things. I used the term "static IP's" as in the kind that Comcast sells, that are public IP addresses. In one of my calls to Comcast support, after describing that I had removed the Netgear router and would just have the SMC unit and a switch, I was confused about and asked how I could get or specify specific or reserved IP addresses for our network printer, time clock and security camera. An earlier call established that the SMC router setup did not allow reserving specific IP addresses related to MAC addresses, as the Netgear unit did. The second Comcast tech said I would need to purchase a bank of five IP addresses from them for these special devices. I asked, "You mean I need to purchase IP addresses from Comcast to re-implement our network printer on our LAN?" And he replied, "Yes", on a couple of occasions. While I certainly am not the brightest bulb in the networking closet, I was stumped by his approach to solving or defining my difficulty. Soon thereafter I put the phone back on its cradle. Obviously, we were mis-communicating.

    Quote Originally Posted by YeOldeStonecat View Post
    Now lots of us setup networks for our clients on Comcast business setups....typically with the SMC gateway. We want to use our own routers for various purposes, and not the SMC gateway. This is very easily done. The proper method is to take the sheet of paper that Comcast gave you, for your static IP block. Take the first usable static IP address...and assign that statically to the WAN port of your own router....and you'll see the default gateway for that IP is 1x number higher or lower...enter that for the gateway, enter your own DNS or Comcasts DNS...and uplink your own routers WAN port to one of the LAN ports of the SMC gateway. You can leave DHCP enabled on the SMC...your router is assigned with a static external interface, and your entire network will plug in BEHIND your own router. So DHCP from the SMC will not impact your own network. What you want to do is log into the SMCs web admin, firewall section, and put a check in the box for "disable firewall for true static IP subnet". Now your own router is not double NAT'd. Your entire network is behind it....192.168.0.xxx, there's just 1 gateway..and your own routers WAN interface is on the proper static public IP address from Comcast.

    And yes the Netgear ProSafe routers will typically be a bottleneck on todays faster Docsis 3 networks....even older Docsis 2 networks of higher speeds. The ProSafes are not very fast.
    Thanks for the confirmation on slower speeds with the older Netgear Prosafe routers. Pardon my ignorance, but in the case like the one I describe (12-14 devices on a LAN in one building), are there problems or risks with just putting the switch after the SMC gateway/unit? Or what are the advantages of adding a newer router in the mix? The only "feature" that we used on the Netgear that I am aware that we lost was restricting Internet access during the wee hours by enforcing rules on a schedule.


    Thanks for your reply.

  4. #4
    Moderator YeOldeStonecat's Avatar
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    Quote Originally Posted by refrost View Post
    I asked, "You mean I need to purchase IP addresses from Comcast to re-implement our network printer on our LAN?" And he replied, "Yes", on a couple of occasions.Soon thereafter I put the phone back on its cradle. Obviously, we were mis-communicating.



    Thanks for the confirmation on slower speeds with the older Netgear Prosafe routers. Pardon my ignorance, but in the case like the one I describe (12-14 devices on a LAN in one building), are there problems or risks with just putting the switch after the SMC gateway/unit? Or what are the advantages of adding a newer router in the mix? The only "feature" that we used on the Netgear that I am aware that we lost was restricting Internet access during the wee hours by enforcing rules on a schedule.
    Yeah that Comcast guy needs to have his head clubbed with a 2x4 a few times.....I work with a LOT of different ISPs all the time...usually Comcast is my preferred one to work with, have good experiences with their onsite techs. Although I work through a few higher up business account reps so I avoid the entry level sales idiots.

    Yes you can put a nice big switch behind the SMC gateway and just use that as your router. I don't use the SMC gateways as routers for my clients...because I use higher end UTM appliances (unified threat management firewalls)....or at the least...I'll have more business grade NAT routers in place that have features I wish....but that the SMC gateway does not have. The SMC gateways perform fine, they're fast, stable. The firewall does basic NAT that things that many businesses will be fine with. However they lack some higher end features...such as VPN endpoints....or advanced port forwarding features (they just do basic port forwarding), or as you mentioned....you had your internet access cutoff for the night shifters. So it's fine for many setups that don't have special needs...but if you have more needs...gotta go get your own router and put it in place.
    MORNING WOOD Lumber Company
    Guinness for Strength!!!

  5. #5
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    How would we do the setup with a Dunamic IP on the Comcast network and a Netgear CG3000DCR? Apparently a Static IP is required in order to run it in Bridge Mode and install another router? Thx

    Quote Originally Posted by YeOldeStonecat View Post
    Yeah that Comcast guy needs to have his head clubbed with a 2x4 a few times.....I work with a LOT of different ISPs all the time...usually Comcast is my preferred one to work with, have good experiences with their onsite techs. Although I work through a few higher up business account reps so I avoid the entry level sales idiots.

    Yes you can put a nice big switch behind the SMC gateway and just use that as your router. I don't use the SMC gateways as routers for my clients...because I use higher end UTM appliances (unified threat management firewalls)....or at the least...I'll have more business grade NAT routers in place that have features I wish....but that the SMC gateway does not have. The SMC gateways perform fine, they're fast, stable. The firewall does basic NAT that things that many businesses will be fine with. However they lack some higher end features...such as VPN endpoints....or advanced port forwarding features (they just do basic port forwarding), or as you mentioned....you had your internet access cutoff for the night shifters. So it's fine for many setups that don't have special needs...but if you have more needs...gotta go get your own router and put it in place.

  6. #6
    Moderator YeOldeStonecat's Avatar
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    I haven't done one of the newer gateways on a dynamic account, our clients are all on static biz accounts.
    MORNING WOOD Lumber Company
    Guinness for Strength!!!

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