Arris 3450 with Orbi RBK50 - DMZ Setup

If you can't bridge the modem, disable ALL wifi radios on the modem, configure the modems DMZ/ExposedHost or IP Pass-Through for the IP address the Orbi router gets from the modem. Then you can use the Orbi router in Router mode.

Or try this:

https://networkgear.review/network-gateway-review/how-to-put-arris-gateway-cable-modem-into-bridged-mode/

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par212 wrote:

Last week I purchased an Orbi RBK50 and had no problems.  Today I was given a new Arris 3450 Modem/Router by my cable company.  This is the first modem/router I have had and wasn't expecting it.  So I looked up the best way to set it up and before even connecting it I logged in and enabled bridge mode.  Once I did that I could not get back into the 3450.  I ended up resetting the 3450 so I could log back in.  The second time I connected the cable to it and logged in and enabled bridge mode again.  After rebooting I got the same result, could not connect to the router but the light did turn green indicating it had internet.  So I reset it one more time.

 

Now with the Orbi still in router mode I connected it to the 3450 but I don't want this double NAT setup.  So this time I tried configuring the DMZ on the 3450 but it is requiring an IPv6 address in addition to the IPv4 before it will let me save.  I have looked and can't figure out what IPv6 address the Orbi is getting.  I have played with the IPv6 on the Orbi but don't see any IPv6 address listed for it.

 

The Arris 3450 has 2604:5c80:201:46a0 prefilled but I don't see anything that start with this anywhere.  Any help on the best way to configure this would be appreciated. 

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