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Tuesday, November 14th, 2023 1:02 PM

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Modem in bridge mode, but (own) router not reachable?

I am a consultant for a commercial entity that uses Comcast Business internet. Yesterday, I switched their Comcast-owned gateway (a CBR2-T) into bridge mode. Now my client’s router (third-party, not owned by Comcast) has an IP address of the form 68.39.www.xxx, while the CBR2-T has an address of the form 73.xxx.yyy.zzz. The support agent I spoke with could not find the 68.uuu.vvv.www address in any of my client’s connection records.

What’s more, I cannot reach my client’s router at the 68.uuu.vvv.www address. The connection is refused. What’s going on? Am I still dealing with double NAT on my client’s router’s WAN interface? Does Comcast block ports?

Problem Solver

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1.5K Messages

1 year ago

Can you ping the 73.x.x.x address?  It shouldn't have one.  It should be a pass-thru in bridge mode.  Admin interface on it will probably also shift to 192.168.100.1 if bridge mode actually worked.  Did you power cycle the Xfinity gateway after you set bridge mode?  It could be, bridge mode setting just didn't stick too.  Their wonky remote-config database arch is problematic.  For buggy equipment, try unsetting bridge mode, power cycle, then reset bridge mode, power cycle to see if you can get it set right. 

Customer's router might need a reboot too depending on how you have it configured, and how it handles the if-down/if-up on router's WAN interface  when the bounces. 

(edited)

2 Messages

@flatlander3​: I haven’t power-cycled the router. I will have to do that. I can ping 73.xxx.yyy.zzz but pinging 68.uuu.vvv.www times out.

Expert

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107.1K Messages

1 year ago

@Garrulus 

Please post your concern in the Comcast Business Class Help Forums here;

https://forums.businesshelp.comcast.com/ 

These forums are for Residential Class concerns. Thank you. Topic is being closed to further replies.

Expert

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107.1K Messages

1 year ago

@Garrulus 

P.S. As an FYI, please be advised that if the customer wants to use the statically assigned IP addresses that come with the Business Class Service, they must use the Comcast-supplied business class gateway device. The RIPv2 or the BGP routing protocols are being used to route the static IP addresses from the WAN to the LAN. Small and medium Business Class customers are on RIPv2. Large customers are on the BGP routing protocol. This gets disabled if the business class gateway is placed into bridge mode.

(edited)

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