Network help!!!

I'm having a network problem and hope someone can assist.  I have Comcast internet and I'm unable to access many URLs.  I can get NCKA and many other sites but can't get to craigslist and many other sites.  It doesn't seem to matter if I'm on an Android tablet or a windows PC.  I have rebooted the comcast modem/router and it didn't make any difference.  I have one PC running windows 7 and one running Vista as well as an Android tablet and a couple of Ipads.  All my devices are having difficulties.  I run Norton on the PCs and it indicates no issues.  I'm stumped!  I'm not an IT guy but have always been able to resolve any issues that come up but not this time.  Suggestions????

Thanks,

Martin

Turn off Norton and make sure it is not blocking as a parental control that may have been accidentally turned on.  Comcast also offers some controls through the web interface.  You can log in to Comcast and look at settings to make sure some blocking settings may have been turned on at that level. 

Comcast usually doesn't block those type of sites but it can be done by user through Norton or Comcast parental controls.

Martin, see if this might help. Does the problem exist with all browsers?

http://windows.microsoft.com/en-us/windows7/why-cant-i-view-some-websites

Martin,
If it is happening to all your devices more than likely it's in the router configuration.  How did you reset it?  If you just turned it off and on it would still used the same configuration.  Most routers have a reset button in the back that you have to hold down to bring it back to default mode.  Comcast support can also help you with that if you are using their modem/router.

Rey

Norton is not the problem since you also have problems accessing certain URLs using iPad and Android tablets. If you are able to access NCKA, but not able to access craigslist, chances are you are having DNS problems. You can test this by using nslookup and ping.

If http://sfbay.craigslist.org/ fails to resolve using nslookup, than it is most likely a DNS problem. To use nslookup,
1) open a command window and type "nslookup" without quotes and press enter.
2) type "sfbay.craigslist.org" without quotes and press enter.
3) you should see 208.82.236.226 as the resolved address. If it fails to resolve, then you definitely have a DNS problem.

You can fix this problem by specifying the DNS servers used for name resolution. Try using public DNS servers:
4.2.2.1 and 4.2.2.2 level 3 public DNS server
8.8.8.8 and 8.8.4.4 google public DNS server
You can change this under your Windows 7 Local Area Connection Properties -> Internet Protocol Version 4 (TCP/IPv4). After configuring the new DNS servers, you should be able to resolve http://sfbay.craigslist.org/.

You can test for network problems by trying to ping sfbay.craigslist.org, or 208.82.236.226. If it fails to ping, then it is a network problem.

Hope this works for you.

Krusty is right on the money;  I suggest manually setting your DNS servers to Google's public, 8.8.8.8 and 8.8.4.4, but i also suggest power cycling your Comcast modem if you havent already. Also, one other thing is that Comcast modems are also acting as NAT firewalls these days. Assuming you go from the Comcast device and into a third-party router, then you may have a "double-Nat" where both devices are using NAT when there should only be one. The default IP of Comcast stuff is 10.0.0.1 with a user name of cusadmin and password = highspeed
You can open a web browser, go to 10.0.0.1 and login, click the Firewall tab and click to disable the firewall and NAT on the Comcast modem. Alternatively, you could login into whatever router you may be using and disable the DHCP server component, then switch the lan cable that normally plugs into the wan port of the router and plug into into any of the four available lan ports. (leaving wan port empty), this using the Comcast modem as your gateway instead. You may have a more complicated setup so you might not want to do this if you aren't sure.

Thanks guys.  It just keeps getting a little weirder.  The problem has fixed itself without me doing anything.  My wife tells me it has be an intermittent problem for a few days.  Could this still be a DNS issue?  I'm going to specify the DNS server as you guys suggested tomorrow.

Martin

I also have Comcast and run into this problem every once in a while.  From your description it's very likely Comcast, not your setup.

I changed the DNS server settings on both PCs and everything appears to be running fine, however it was OK this morning without the change.  Thanks for the help.  NCKA is far more than a kayak/fishing club!

Martin