Arris: DHCP Reservation

Note: for DHCP Reservation, after you click on LAN Setup, you click on Client List, NOT DHCP.

Okay cool, so to recap, I should do this dhcp reservation step first before I go into the port forwarding step. And DO I have to hard wire my computer via Ethernet to the e4200 for this dhcp reservation while having my Xbox turned on and connected to the
e4200?

Thanks

There is some indication that a TW tech can put the Arris in bridge mode or that you can do it yourself by logging in immediately after resetting it to defaults:

www.dslreports.com/.../r27274883-TWC-Does-anyone-else-have-an-Arris-DG860a-modem-

Alternatively, see if TW will provide a modem only or buy your own (cheaper than leasing in long run and gives you more control). Failing that, assuming you can configure port forwarding, DMZ, etc. on the Arris, you have a couple options. First, with the
Arris connected to the WAN port of the N900, you could try putting the WAN IP of your N900 (this should be a private IP received from the Arris over DHCP) in the DMZ on the Arris (delete any other forwards on the Arris). Do all port forwarding and DHCP as
usual on the N900. Or, second, you should be able to use the N900 as just a switch + wireless access point (bypass NAT routing) by disabling DHCP on the N900 and connecting the Arris to a LAN port on the N900 rather than to the WAN port. All NAT, port forwarding,
and DHCP would then be provided by the Arris.

Personally, I would just get a modem only, such as the Motorola 6141 (if supported by TW).

An open NAT is no guarantee that this behavior will be consistently open for each endpoint on your network.

Can you see if your router support DHCP reservation, or IP reservation. If so, setup both console's to have their IP address reserved in the DHCP of your router. Before you setup this, make sure you reserv a unique IP outside of the DHCP's dynamic IP pool
range.

Is there any chance you can try with a wired solution?

You do not need to reserve an IP using DHCP reservation with a router that is well-behaved.