I'm looking for advice on how to set up DNS, web, and eMail servers on a cable modem.

I recently moved, losing my DSL line with static IPs that I had used to run a low-level web hosting company (actually an elaborate hobby). I had run my own DNS, mail, and web servers. The only high speed option in my new home is Comcast cable, where I can choose either the $45 "home" version (with terms of service that prohibit me from running servers) or the $90 "business" account (which would let me do whatever the heck I want). On the business account, I can pay an additional $30 for a single static IP.

Being a cheap b*stard (and having a wife!) I want to go as cheaply as possible.


Here is my plan so far:

Since the dynamic IP address is "persistent", I figure I can get by without the static IP. I'll just have to change the master DNS entry in Register.com's servers whenever the IP changes. My servers may be effectively offline for 24 hours or so whenever the IP changes, but as long as this doesn't happen more than once every month or so, I'm OK. I'll put the router on a UPS and ping the network to keep the connection alive, thus maintaining my IP as long as possible.

If comcast doesn't filter/block port numbers, I'll just ignore their terms of service and run the servers anyway. My traffic volume is low enough that nobody at comcast will notice the bandwidth.

If comcast does filter/block port numbers, I'm stuck with the $90 business account.


My questions for the group:

1. Is a "persistent" IP good enough? How often to cable companies actually reassign dynamic IPs?
2. Do cable companies (comcast in particular) filter/block critical ports such as those used by DNS, eMail, and web servers?


TIA! Please reply here as my eMail address is down since my servers are offline

You can use a dynamic IP address service like dyndns.com or noip.com. They have clients that run your computer that will update their DNS with your IP address.

I use a Comcast home account and have a box running as a web, ftp and ssh server. So far I've had no problems with blocked ports. The IP address has also been remarkably stable. It does change from time to time, but I bet it is easily 2-3 months between IP address changes and even then it seems to be precipitated by a larger event such as a power outage or me taking down my router for a bit.

Comcast user here as well. No problems with blocked service ports, but I think it's only a matter of time before they start policing their network. Therefore, I run apache on a highport and simply use no-ip.com webredirect feature so that http://mydomain.no-ip.com redirects to http://mydomian.no-ip.com:8000.

I've run multiple servers off of my Adelphia cable modem for a while now. They blocked port 80, but I simply set up a redirect using Zoneedit. I have no problems with ports 25 and 110 (SMTP and POP).

There is something you should be warned about, though. Cable modems essentially are set up to be on one big LAN. In other words, the cable system basically acts as a different network medium (as opposed to typical Ethernet cable) that travels farther. You encounter some problems here with running a server.

This is the way things are where I am with Adelphia, Comcast might be different, I'm not sure. But essentially the way things are set up (a friend used to work at Adelphia), you're bassically sharing something a little faster than a T-1 with a whole bunch of other people. While you get very good download speeds, the upload speed tends not to be very good. It can also degrade as more people use their connections. In addition, if too many people upload files at the same time, it can cause serious network traffic, and clog things up temporarily. That's why a lot of the time cable companies are reluctant to let you run a server from their connection.

If possible I would advise going for the business account; that way you can probably avoid low upload speeds. If you were simply using this server for a personal site, though, you could get away with the regular account. How much traffic do you expect, and what's your content like?

As for the IP address, it should stay as long as you don't reboot your modem.

Well, I'm on comcast and everything works just fine. No ports are blocked. Speeds are better than I was getting with upgraded business DSL. Things are both "hunky" and also "dorry".


My IP has been stable for a few weeks. I put a cheap UPS on the cable modem, so it should stay up even if the power fails for hours (which is pretty rare) and hold my IP lease.

// begin I love comast rant

I love comcast.

Ive been on the network for about 2 years, and in that time my ip has changed twice. one of thoes two times was when i replaced my router. w00t! If I wasnt lasy, a mac address clone would have probally kept my ip for me :P



no ports blocked, and its fast. uptime is i would say 99% or better.

no-ip.com is a great service, and i have used it, but as often as my ip changes, Its wasnt worth the effort to install it last time i did a format.



When i signed up for this service, it was 1.5 down and 128 up. They sent me an email a year later saying "by the way, we are doubling your upload speed for free" which made me VERY happy (i run a small game server somtimes), and a few months later saying "hey, we are going to double everybodys download speed too.

Needless to say, comming from verizon dsl (which sucked ass btw) im going to be a comcast customer for a long time if they keep their policies as they are

// end i love comcast rant



//being other usefull info

as far as a setup, just foward the ports from your router to your linux box. It would be a good idea to give the linux box a internal static ip, but as long as you dont reboot the ip wont change anyway.

the apache server should be easy enough to set up, just edit /etc/apache/httpd.conf and do a apachectl start.

Ive never done mail servers


ssh is easy too, just install it, and edit its config file to dissallow root login and change the protocols line from (2,1) to (2) (security tweaks)

// End all usefull info


Have fun, and enjoy your new line


//comment to jeremy
Oh and jeremy, i keep trying to post by hittign ctrl-s ctrl-c. you really should make some kind of hack to make that work on the forum so I can feel l33t instead of retarded

So Comcast has no problems with you running a server? That's nice. Adelphia hasn't done anything about my servers aside from blocking the ports. Still I'd love to have a nice fast symmetrical DSL line...

Well, after a few weeks more, I find that some of my out-bound mail is being filtered (by aol). I presume it is because my mail server is on one of those spam-infested IP's used by cable companies. <sigh>


Anybody know of a good public secure relay service?

oops

Ooh! How do you clone a MAC? I have an extra cable modem rotting in a box...

I've had this problem myself. Depending on your provider you may be able to bounce all your outgoing mail off your ISP's server, though that might be blacklisted also. It's worth a shot, though. Check out this thread.

Good luck!

Relaying through comcast's mail server worked just fine. Thanks for the suggestion!