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daveotto's profile

New Member

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3 Messages

Mon, May 20, 2019 8:00 AM

Can I isolate two wired subnets?

I can handle simple network setups but have no experience yet with what I want to do:  I want to, behind my comcast business gateway, set up two different wired subnets which cannot access each other.  How simple (or not) is this?  Can I just plug a second switch or router into a different plug on the back of my comcast gateway and expect them to be isolated from each other?  How about if I have two routers, set one as, say, 192.168.1 subnet and the other as 192.168.2 subnet.  Would they then be isloated from each other?

 

TIA,

daveotto

Responses

Official Employee

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1.1K Messages

2 y ago

HI daveotto and welcome to the business forums. 

 

I appreciate you posting your question on your network. Since this does deal with your personal network, I am not able to say much on this due to our demarcation policy. However, I can say that this would be entirely dependant on what you're trying to accomplish and how you have your current network. Are you currently using the leased gateway in bridge mode or passthrough mode?

 

https://forums.businesshelp.comcast.com/t5/Equipment-Modems-Gateways/True-Bridge-Mode-vs-Pass-Through-Mode/m-p/21260#M2402

 

Multiple DHCP's within a single network could cause some conflict. 

Official Employee

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348 Messages

2 y ago

I understand what you mean and are you using a static IP by chance? If so, you would not want to run bridge mode. 

New Member

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3 Messages

2 y ago

Hi Comcast_Phil,

 

It's not in bridge mode, it's functioning as a normal router right now.  I also have a single router behind it, and there is forwarding from the gateway to my router, then from there to my surveillance DVR so I can check it from home.

 

I know, I could use bridge mode and just forward once, but I always expected that someday I would put another router back there and keep two different isolated subnets.  Basically this is because I will have somebody working in my building for some time who needs (wired) internet access but I want to make it impossible or at least pretty tough for them to get at anything on my main subnet.

 

Thanks,

DaveOtto

New Member

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3 Messages

2 y ago

No, it's not a static IP, it's standard comcast dynamic.

Contributing Member

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128 Messages

2 y ago

daveotto, I've checked a few networking forums and it looks like you can do so if you enable NAT on both modems.