Unable to connect

[ronaldhanko]

Should have mentioned that the problem was not with Comcast (though for all I know it may have originated with them and they did help me track the problem to my router), but with my Netgear router and its settings.

[RosieC]

Although I find it strange that two of our members on Comcast have both had the same problem at the same time However I'm starting to wonder if the problem is that one (at least one) of Comcast's IP addresses is on blacklists. Howard's current IP has been traced to at least RBL's ("realtime block list").

That's not Comcast's fault, that's the fault of people who have paid for their service and then abused it. Even BT, the biggest telecom provider in the UK, has various IP's on black lists and we keep hitting a problem with that where I work.

I'm wondering with my limited knowledge of this stuff, if the changes on the router were enough to trigger it to get another IP from Comcast's range and that new one is not a problem. I don't know, just a guess from what I've read about Howard's problem.

[ronaldhanko]

It is strange that we're both on Comcast and both had the problem but you are probably right about the reason.

[Discus]

Depending on how Comcast is set up, turning off a router for about 1/2 an hour (sometimes even just off and on again) will often lead to you being given a new IP address. Pretty much all ISPs use something called DHCP to assign an IP address ("lease") to your router from a "pool" of addresses. Essentially, your router has what is called a MAC address, and it sends a query out to your ISP's server asking for an IP address; the server then notes the MAC, and sends back a message saying "here's your IP address, and it's yours for <period of time>". MAC addresses (which consist of 48 bits) are usually expressed in a counting system called hexadecimal, and usually look something like 00:1A:A0:C7:E0:00. Every single device that works on an ethernet network (wireless, wired, fiber etc) has a MAC address. This means there are approximately 2.81474977 × 10^14 possible addresses - 281,474,977,000,000 of them! (the exact number is 2^48, but a lot of calculators round things hence the zeroes above). IPv6, which you may have heard about is a 128 bit number, which gives a number so large it's quite hard to write out (IPv4 is 32 bit).
If you're interested:

"I wanted to make a cool graphic to show the relative sizes of the IPv4 and IPv6 address spaces. You know, where I’d show the IPv6 address space as a big box and the IPv4 address space as a tiny one. The problem is that the IPv6 address space is so much larger than the IPv4 space that there is no way to show it to scale! To make this diagram to scale, imagine the IPv4 address space is the 1.6-inch square above. In that case, the IPv6 address space would be represented by a square the size of the solar system."

After this time elapses, the client (your router) has to renew the so-called DHCP lease for an IP address (many DHCP servers hand out leases for fairly long periods of time; some may be only a few minutes - it depends how limited a pool of IPs your ISP has and what their customer online "churn" is like - in the days of dialup, pretty high, nowadays with always on, pretty rare. Typical leases are 24h to 7 days.) Usually, this renewal request results in the same IP, but not always (C: Hi, can I still have this IP? S: No sorry, I gave it to someone else, have this one instead. C: Ok, thanks!) This IP change is one reason why services like DYNDNS are so useful for home users who want to have their computers accessible on the internet - DHCP assigned IPs change, which breaks all sorts of things - it's like having your address changed - all your mail gets lost! Dyndns tracks your changing IP (basically, your router keeps telling the service what your IP currently is) and so you can pretty much always connect to your services. To make this work, dyndns's DNS records have very short TTLs
.

It's entirely possible that one IP you're assigned is allowed access to OB, whilst the next is on a list of miscreants, because as Rosie says, some idiot abused that IP in the past. This lease renewal can even randomly coincide with you doing something on a site that is then affected, making it look like "the last time I posted on OB... it broke!".

It would be interesting to find out from Marty or HostRocket whether either the OB software/server implements some RBL (to cut down on comment spam for instance) or if it's a HostRocket enforced customer protection service. Marty would be best placed to let us know, as I imagine he knows OB's software and its tweaks, and as a customer, can ask HostRocket what the deal is.

Ron - do you perhaps recall if it was a setting in the "firewall" area of your router (or did they have you change tons and tons of stuff?), or did they get you to perhaps change the MAC address to essentially force a new DHCP lease (and likely a new IP)? I don't have a netgear router here to check what netgear calls these things.

[RosieC]

Someone else has reported on the facebook OB post that Howard made that he's also not been able to get here for a week and he's also with Comcast.

Discus, that's a much better description of what I vaugly understand. My hubby is the one who knows about these things and I just have a vague understanding from what he's explained to me.

I know we work on about an hour for turning off our router if we want to get a new IP here at home, but as you say, sometimes you still get the same one because they've not re-allocated your old one yet. I think that may be Howards problem. Comcast told him to reboot the modem to try and get a new IP, but it may not have actually happened. (Although again I'm just guessing).

[Discus]

Rosie - could you perhaps direct Marty's attention at this thread/issue and ask him to investigate in depth? With 3 known "casualties" it's something that needs to be dealt with. It will probably be helpful in troubleshooting the issue if the "casualties" can supply the IP address assigned to their router and time(s) when the problem occurred.

I deal with quite a lot of networking stuff (at times I find it almost as interesting as orchids ), and consider myself as having a fairly advanced knowledge of the topic, but I'm still learning!

[RosieC]

I will do, however I've already told him that three people have had the problem, and he's confirmed there is no block in his software and has suggested some ideas, none of which have worked for Howard.

From what I've read on the facebook posts someone has looked at the route trace from Howard and it's getting stuck at the interface between Comcast and HostRocket (the ISP hosting OB). If that's the case then it's getting stuck before it even get to the OB servers so there will be little Marty can do. Although it's always possible I've mis-understood that.

If you are on facebook then take a look here at the most recent discussions on this.

[Discus]

Yeah, it was me that was asking Howard for a traceroute - I asked him to paste the entire thing in there, but he didn't (it's a bit tricky, you have to know about the Mark right click command and how to get that into the clipboard) - I *thought* it was at the border of HostRocket's AS, but wasn't totally sure, as his description was a little confusing.

My understanding of Internet routing (I may be wrong) would indicate that if ComCast lost their peering with HostRocket (or some 3rd party intermediate transit) it would manifest this way - however, if Ron and others got back again (and comcast tech support said they could get there), that would suggest that a loss of peering session would not be the problem at all.

It may be worth resetting the router of the afflicted party to factory defaults - this page tells you how to do it for Netgear devices HOWEVER they *must* know/find out/note down their Comcast login details. I've never used a cable modem, so I'm not sure what options there are; there should probably be a login - although my quick googling suggest Comcast does all the authentication solely from the cable modem's MAC address so this is less of a concern.

Cable modems have a coax jack on the back of them and use a protocol called DOCSIS; "normal" broadband modems use ADSL and have an RJ11 style telephone jack on the back. This is a netgear cable modem:

Comcast also offer a more fully featured service (Xfinity), which has a more complex device. Complexity often means "more trouble"!.

I suspect most home cable modem installs look something like this:


Which means you have several potential troublespots
1) the site you're visiting
2) your computer
3) the additional router/switch
4) the cable modem
5) some crazy problem with your ISP's connection to the internet

1-4 you can usually do something about. 5, not so much. 1 can also be tricky.

Each of these scenarios needs to be checked and ruled out.

[camille1585]

Oohhhhh, so you're the guy posting all the troubleshooting advice! I don't know why I didn't recognize the your name from when you gave me your email address to send the Nature paper!

[Discus]

Indeed Thanks again for that paper.

Incidentally, there are loads and loads of potential cable modem devices on Comcast: DOCSIS Devices
and of course, even more options for 3rd party routers plugged into that...