Bridge Xfinity Arris gateway to Synology RT2600ac router

[sbernie2]

Hi, as part of a saga to solve a problem where my DNS suffix was "hacked" (see here: https://forums.xfinity.com/t5/Your-Home-Network/quot-Utopia-net-quot-DNS-suffix-coming-from-router/m...), I am trying to bridge my gateway from Xfinity to another router. This was advised by an Xfinity repair tech as the only other thing left to try.

I have a third part router from Synology. I have followed the steps in the Xfinity help page about putting my gateway into bridge mode (here: https://www.xfinity.com/support/articles/wireless-gateway-enable-disable-bridge-mode). I have also done the basic Synology setup of creating an admin account for the router, wifi name, password, etc. The bridged gateway is connect via an Ethernet cable in Port 1 to the WAN port of the Synology router. My PC is connected via Port 1 of Synology.

However, I'm not getting any internet. Help forums for Synology seems to imply it would be mostly plug-and-go, so I'm confused. It is possible that I need to fill in a section labelled "ISP settings" because the new router has been unable to do this itself. Unfortunately, I don't know what it's looking for in "DHCP client", "hostname", "MAC address", etc. Which MAC, router or modem? How do I determine DHCP client? Is there something else going on?

Any suggestions? Thanks.

[jweaver0312]

Unplug both devices. Plug the gateway back in and let it boot up all the way. Then plug the Synology back in. Any changes?

[sbernie2]

Nope, tried that already with no changes.

[jweaver0312]

Are you able to try to reset the Synology to factory defaults and go through setup again?

Also, is the firmware on the Synology up to date?

[EG]

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@sbernie2 wrote:
Nope, tried that already with no changes.

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Is the WAN interface in the router getting assigned a public IP address from the modem ?

[sbernie2]

It does not appear to be, no. When I log into the router's interface, under Network Center is says Internet Connection - Disconnected with the IP Address field blank. It's using the Comcast DNS server I specified for it.

[darkangelic]

Try connecting your PC directly into the Bridged gateway and see if you get an IP address (make sure to reboot both devices first before connecting). 

[sbernie2]

I get an IP when my PC is connected directly to the gateway that's in bridge mode. Weird?

[RobertWy]

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@sbernie2 wrote:
I get an IP when my PC is connected directly to the gateway that's in bridge mode. Weird?

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Not weird; Bridge Mode disables the gateway wifi.

https://www.xfinity.com/support/articles/wireless-gateway-enable-disable-bridge-mode

[sbernie2]

Also, @jweaver0312, I tried cycling both devices through factory resets, with no luck. The router is up-to-date. I did find some info in the gateway's admin controls and it seems able to connect to the Xfinity network fine, but it doesn't "see" the Synology. Also found various MAC addresses but I'm pretty sure they are for the gateway and do not apply to the missing info in the router settings.

[EG]

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@RobertWy wrote:

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@sbernie2 wrote:
I get an IP when my PC is connected directly to the gateway that's in bridge mode. Weird?

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Not weird; Bridge Mode disables the gateway wifi.

https://www.xfinity.com/support/articles/wireless-gateway-enable-disable-bridge-mode

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For clarity. It also disables the gateway's NAT / DHCP / routing functions. It then acts as a plain vanilla cable modem / layer 2 bridge that bridges the public IP address that Comcast's DHCP server provides to the connected client device.

[jweaver0312]

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@sbernie2 wrote:
Also, @jweaver0312, I tried cycling both devices through factory resets, with no luck. The router is up-to-date. I did find some info in the gateway's admin controls and it seems able to connect to the Xfinity network fine, but it doesn't "see" the Synology. Also found various MAC addresses but I'm pretty sure they are for the gateway and do not apply to the missing info in the router settings.

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As a test, try setting it up behind the gateway while leaving the gateway in router mode to see if it picks anything up.

Also, try plugging the computer in again while the gateway is in bridge mode and open the connection information. It should give you the IP, Subnet Mask, etc. Take a screenshot of that screen and copy all of that information into the Synology including the MAC Address.

[sbernie2]

I do have that info from my earlier experiments. Which MAC though?

[jweaver0312]

I would plug in the MAC Address of the computer you used to attempt. See what it does.

[sbernie2]

Ok, so I hit "clone" in the MAC address field of the Auto ISP Settings for Synology. This auto types in the MAC address of my PC's Ethernet port. I swear I tried this before, but for whatever reason it worked this time. After applying the change, I now have internet - but only wireless. Ethernet isn't working.

Any suggestions as to how I can get Ethernet? Going to wander around Synology's settings to verify there isn't an on/off button for it and try different ports on the router.

Thanks for help by the way.

[sbernie2 · Accepted solution]

Never mind, it appears that the router just didn't like Port 4. Will test if port is broken later, but it appears that the problem is solved.

Solution: Use the computer's MAC address in the ISP settings, and probably reboot things a few times.

Thanks, All!

[jweaver0312]

Yeah. When the gateway is in bridge mode, you need to use Port 1 to connect to the WAN port on Synology.