Comcast router

Running a Small Business Server 2012 Essentials with 7 users
We also have several NVA security camera systems. After creating a few passthroughs that would not work properly we would call Comcast support, support would do some changes and the passthroughs would work just fine. I'm not sure what they did to get it to work, I assume they simple allowed certain ports.

A couple months ago I had to add another passthrough but again it would not work. I called support and this time they could not get the passthrough to work properly so they recommended I use my own Router, Comcast support turned the Comcast router into bridging mode and  I installed a Linksys LRT224 and configured all my passthroughts. Everything worked just fine. My new Linksys router would answer to
 DHCP on the Linksys router is turned off and my SBS2012 server is doing DHCP and DNS.
Today I'm having network issues, if I go to the Comcast router comes up and not my Linksys.
I called Comcast support and all they can tell me is that my Comcast router is still in Bridge mode. I removed the Linksys and now my Network is running ok but of course none of my passthroughs are working.

Question if my Comcast router was set to bridge mode wouldn't I lose the internal address

Any suggestions are appricated
jsarinanaI.T. ManagerAsked:
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Joshua HopkinsPresidentCommented:
Ususally when the comcast modem is set to bridge mode you lose access to the web gui for it.  I would call comcast and have them adjust it.

Alternatively you can change your internal network schema to something other than 192.168.1.x to something else.
jsarinanaI.T. ManagerAuthor Commented:
When Comcast changed it to bridge mode I did lose my gui, then I setup my Linksys with schema Now the Comcast router responds to
Fred MarshallPrincipalCommented:
I have seen cable modems come up in one of two modes.  I've never figured out (or tried to figure out) how this is supposed to work.  But here is my empirical model of it:

- Set up a cable modem for the first time or with nothing connected to the LAN.  Connect a laptop.  Sometimes the cable modem will then present itself with a private LAN address and DHCP such as and addresses.

- Set up a cable modem with a router or a laptop and after a reboot of the modem, it will provide a public IP address.

As I said, I don't know how to force them to switch modes.  

One sure "tell" that this could happen is if the modem has but one Ethernet LAN port.  
If it has more than one LAN port then it expects to deliver multiple private addresses is my belief.

What you want to do is to make all this immaterial.  It appears you've already done that.  My rules are:

Install a router with an unusual LAN subnet like or or .....
And the WAN side to get its address via DHCP from the modem.
With this in place, the likelihood that the modem or modem/router having the same subnet on its LAN port(s) is very low.  You don't want them to match.
And, if the modem is ever replaced then there's really nothing to be "fixed".
It doesn't matter if the WAN address on your router is public or private as far as your LAN goes.

If the modem LAN is on a private subnet permanently then you will have to worry about port forwarding in the modem/router if port forwarding is needed.

Another way to describe the two "modes" that I mention above is whether the modem/router is providing NAT or NO NAT and NO NAT may be referred to as Bridging Mode.  So, what I've experienced seems to be an observation of the modem changing from NAT to Bridged - whether that's automatic/local or somehow controlled by handshaking with the ISP end is a question....

I don't know what you mean that "the Comcast router responds to".

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jsarinanaI.T. ManagerAuthor Commented:
I don't know what you mean that "the Comcast router responds to".
I mean the address gives me the Comcast router gui. used to give me the Linksys router gui that's when everything worked correctly.
Fred MarshallPrincipalCommented:
Well, that's very interesting.  I wouldn't have thought that the Comcast would have an address like that.
But then, it's not all that "unusual" a subnet or perhaps I should say "imaginatively unusual" as compared to something like

What are the IP addresses on the LAN now?

When you can get into the Linksys, it would be interesting to see the Status page.
It would also be somewhat interesting to know what happens if you hook a laptop or other computer up wired directly to the Comcast device.
There's a bit of a mystery here that needs a bit more illumination.
jsarinanaI.T. ManagerAuthor Commented:
I found the Comcast router still had a DHCP service running, as soon as I turned it off things started to work properly
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