Attention All Cable Internet Subscribers: A Tech Support Request

After spending six days at CES, I unfortunately had to turn around and head back on the road less than 24 hours after getting home Sunday evening. As I write this, I’m in Indiana due to a family emergency. And while I’m here, my sister and her family have also recruited me to do some consumer electronics setup for them.

Impressed with the Xbox 360 I brought home for the holidays a few Christmases back, they subequently obtained one of their own, but they’ve never been able to get it online with Xbox Live. They’re Comcast cable television and Internet subscribers, and until today they’d direct-connected their Arris TM402P/110 cable modem (which, at minimum, apparently also acts as a DHCP server) to their PC over CAT5 cable. I drove down to Radio Shack and bought them an on-sale (albeit still obscenely overpriced) NETGEAR WGR614 (the non-open-source version of the WGR614L), CAT5-inserted it in-between the cable modem and PC, loaded up the router’s web browser-based configuration screen, and cloned the PC’s MAC address.

The good news: both the PC and Xbox 360 (along with the wirelessly tethered laptop I’m using right now to publish this writeup) are now online as well as communicating with each other. UPnP also seems to be working, since the game console claims (and acts as if) it’s Xbox Live-connected, and I can see from the router status report that it’s opened UDP port 3074 (albeit none of the other documented required ports, at least not yet) in the router’s firewall. I’ve even set up a DynDNS domain name for the family, which the router automatically maintains as the dynamically assigned WAN IP address from Comcast changes.

The bad news; the router configuration screens include one that optionally enables WAN access to the router. I’ve got it enabled, so that in the future I can work my tech support magic from afar. But I still can’t seem to access the router, no matter what port I configure (so far I’ve unsuccessfully tried 80, 8080, and suspecting that Comcast might be blocking incoming traffic over commonly used ports, 81). This is the case even though if I enable a different setting that allows the router to respond to ping attempts, I get the anticipated ACKs (i.e. ICMP echo responses)…and if I subsequently re-disable the ping setting, the ACKs cease, confirming that I’m using the correct WAN IP address.

This same no-WAN-access problem happened a few weeks ago as I was debugging a different router (Apple’s Airport Extreme ‘N’) owned by my neighbors and friends the Lessers. The Lessers have a different ISP (Suddenlink) and different cable modem manufacturer and model (Ambit U10C018). But that I’ve run into the same issue with consecutive cable Internet setups leads me to suspect that I’m running into some sort of cable Internet ‘feature’ which I as a long-time DSL subscriber have never personally stumbled across. Your insight is welcomed; thanks in advance!

Followup: Fixed, and I confess I feel a bit foolish. In the past, with the innumerable routers that have passed through my life to date, I’ve usually been able to access LAN resources (including the router itself) via the LAN’s associated WAN IP address even when I was behind the router (i.e. when I was on the LAN). Occasionally, however, I’ve encountered a router for which the WAN IP address doesn’t work unless I’m on the WAN. The Linksys WGR614 is apparently one of the latter (at least for HTTP…as I mentioned in the main writeup, ping attempts to the WAN IP address from behind the LAN work without a hitch). On a hunch, I connected to the Internet via my Verizon EV-DO card, attempted to access the router that way, and had no problem. Sorry!