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Comcast XB3 / Cisco DPC3939 Gateway - Can't connect to external router (RESOLVED)

B

bmacd

Lifer
Hello!

Bottom line up front: I bought a new router to use with my now-bridged Comcast gateway, but I can't connect to the internet. Using an ethernet cable direct from the gateway to the computer works flawlessly.

Based on recommendations from AnandTech Networking, I purchased an ASUS RT-AC66U router to replace the router functions of my Comcast-branded Cisco XB3 gateway. I called Comcast and they put the modem into bridge mode. I can successfully connect to the internet using an ethernet cable direct from the gateway to the computer.

I cannot, however, get my new router to pick up an IP address using DHCP. The tier-1 and tier-2 Comcast representatives assured me that the problem was not on their end and this was definitely a problem with my router. So I grabbed two other working routers, and neither are functioning with the current setup.

Any ideas?

RESOLVED :

After spending 1.5 hours with Comcast Tier-1 and Tier-2 support last night, they concluded that it was an equipment issue. I called this morning, and a Tier-1 helpdesk'er resolved the issue in 15 minutes. With my Comcast XB3 (Cisco DPC3939), they had to manually disable both of the wifi networks that the gateway was broadcasting. As soon as she did that, my routers were able to grab an IP using DHCP within seconds. Thanks for everybody's assistance last night.
 
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What is the IP of the computer when you are connecting Directly to the Bridge and you do have a working Internet connection?



😎
 
I'll check the IP later on. Yes, I do have a working connection when connected via Ethernet cable from the gateway (not the new router) to the computer.
 
Hook up the router to into CommyCast's equipment, and hook up your PC(s) into the router.
Power cycle the modem.
(You can either reboot your PC or do ipconfig /renew)
Wait for the modem to sync (all lights will be solid when done).

When it syncs, the ASUS should now have gotten a DHCP response.
All should be working.

If not, you go to the router's home page (192.168.1.1 I think it is) and look under logs to see what it is saying.
 
I'll check that as soon as I get home. Is there a Mac-equivalent to IPCONFIG? Also, is there a way to identify if this is a Comcast issue or a customer-provided equipment issue?
 
bmacd said:
I'll check that as soon as I get home. Is there a Mac-equivalent to IPCONFIG? Also, is there a way to identify if this is a Comcast issue or a customer-provided equipment issue?
Click to expand...

Most likely, but, usually easier to just reboot the mac. 😉

As to find the problem, assuming after the modem reboot it didn't work, the router's log will say something about unable to get DHCP response. If that is the case, then, the problem is comcast's equipment, so they need to set it to bridge mode, and reboot it.
 
Elixer said:
Hook up the router to into CommyCast's equipment, and hook up your PC(s) into the router.
Power cycle the modem.
(You can either reboot your PC or do ipconfig /renew)
Wait for the modem to sync (all lights will be solid when done).

When it syncs, the ASUS should now have gotten a DHCP response.
All should be working.

If not, you go to the router's home page (192.168.1.1 I think it is) and look under logs to see what it is saying.
Click to expand...

"WAN Connection: ISP's DHCP did not function properly."
 
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