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Arris 8200 connected to Xfinity coax only has external IP

  • September 24, 2023
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The Many
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Set up the Arris8200 with Xfinity Internet coax, plugged network cable to a port on the Arris8200

i am able to get an IP from arris, however, the IP is an external routable IP,  there does not seem to be configured a LAN, internal only IP which I would have expected 

 

I cannot access 192.168.100.1, as the IP I have been allocated looks to be directly from Xfinity, and I am unable to add anything to the second network port on the back of the Arris8200 as the DHCP looks to be provided direct from Xfinity

 

how can I get to configure the Arris8200 when it appears to be not doing its own DHCP for an internal network but rather passing DHCP from Comcast?

 I requested help from Comcast who said to contact Arris directly for help…

 

 

Best answer by LoveMyLab

Should not need to specify the port. As you noted, you basically have to make a choice. If you only want to connect a single PC to the 8200, that will work fine and you can browse the internet or hit the web console at 192.168.100.1. If you want to have multiple devices, and/or want WiFi, then you absolutely need the router. The router will typically be 192.168.1.1. It will handle DHCP then. You still should be able to navigate from your PC via the router to 192.168.100.1. If you see a failed/timeout, that usually means a VPN or firewall issue in my experience. I know how interesting it can be working in somebody else’s environment!

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LoveMyLab
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  • LoveMyLabGuardians of the Gateways
  • Guardians of the Gateways
  • September 24, 2023

I’d like to help if I can, so let me ensure I’m understanding the configuration and the error(s) first. First, there are 2 ethernet ports on the back and you would only use both if you are doing link aggregation. 

When you connect your PC via ethernet directly to the top ethernet port, it sounds like you are unable to navigate to 192.168.100.1. What error are you getting? Can you ping it? That’s the first thing to sort out.

 

Once that is sorted out, what sort of network configuration are you planning? Are you just going to use the PC, or are you planning on using multiple devices? If multiple devices, you’ll need an appropriate router that will handle the DHCP for the local network, with or without WiFi based on what you are trying to do. I use a primary Google WiFi router and both “unmanaged switches” and WiFi satellites to extend the network.

I use: SB8200 > Google WiFi > 2 D-Link DGS-108 > 4 Google WiFi with ethernet backhaul.
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Hello LovemyLab,

thank you for your time and reply.  On poking further, it looks like the Arris surfboard has just been configured to pass the external IP to our WiFi router, which is odd to me, as I had expected a LAN enabled port to be available on the a surfboard.

 

instead , our WiFi router has the external IP, and the port on the Arris it is connected to does not appear to be the advertised gateway (that looks to be Xfinity’s

 

is this by design?  I am not too happy not being able to connect to the arris to run diagnostics or view logs 

 

its been a good while since I’ve configured anyone’s network with Xfinity - so maybe they have it under their control only?  
 

(or is there a port I should have used in the URL and missed?)

 

Thanks again for your time in trying to help out my parents 😅

LoveMyLab
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  • LoveMyLab
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LoveMyLab
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  • LoveMyLabGuardians of the Gateways
  • Guardians of the Gateways
  • October 1, 2023

Should not need to specify the port. As you noted, you basically have to make a choice. If you only want to connect a single PC to the 8200, that will work fine and you can browse the internet or hit the web console at 192.168.100.1. If you want to have multiple devices, and/or want WiFi, then you absolutely need the router. The router will typically be 192.168.1.1. It will handle DHCP then. You still should be able to navigate from your PC via the router to 192.168.100.1. If you see a failed/timeout, that usually means a VPN or firewall issue in my experience. I know how interesting it can be working in somebody else’s environment!

I use: SB8200 > Google WiFi > 2 D-Link DGS-108 > 4 Google WiFi with ethernet backhaul.

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