IPv6 DNS configuration

As an IT professional, I’ve long been aware of the impending IPv4 exhaustion. To the layperson, this can easily be compared to phone numbers… there are now so many devices connected to the Internet that the size of the number used to identify and reach each of them uniquely is impossible.

IPv6 is a newer addressing system that supports a drastically increased number of addresses/numbers for use. Unfortunately, like Digital TV (in the US), adoption and migration of users and websites is slow.

To do your part as a user, you can change the settings in your gateway/router/modem to allow for IPv6 DNS lookups as most providers already support IPv6 traffic.

You can test your connection here:
http://www.test-ipv6.com/

Here are a few common values, I’ve also provided the Comcast/Xfinity values for reference:

OpenDNS IPv4:

  • 208.67.222.222 (resolver1.opendns.com)
  • 208.67.220.220 (resolver2.opendns.com)
  • 208.67.222.220 (resolver3.opendns.com)
  • 208.67.220.222 (resolver4.opendns.com)

OpenDNS IPv6:

  • 2620:0:ccc::2
  • 2620:0:ccd::2

Google IPv4:

  • 8.8.8.8
  • 8.8.4.4

Google IPv6:

  • 2001:4860:4860::8888
  • 2001:4860:4860::8844

Comcast IPv4:

  • 75.75.75.75
  • 76.76.76.76

Comcast IPv6:

  • 2001:558:feed::1
  • 2001:558:feed::2

REFERENCES:

Comcast Business Class gateway forwarding port 22 for SSH

For as long as I’ve had Comcast, and other providers for that matter, I’ve been able to configure my internet gateway/router to allow port 22 (SSH) access to an internal machine. It came as a surprise to me earlier this week that I was blocked when I tried to use their web admin console to change the internal forwarding to a newer machine. As usual, Technical Support was less that helpful and said that it was not possible to do so, and never should have been as Comcast uses that port to administer the gateway. To make matters more disturbing, I was told that I could not have similar SSH access to the gateway, and that replacing their hardware, while permitted, would prevent my use of a static IP.

Back to the solution, as I know that I had only setup this forwarding about a year ago, and it was working only minutes before I tried to change it, I knew that the configuration was possible if I could figure out how it was being blocked. The message in the web console was a javascript alert(); and gave me a starting point. I opened up Firefox and used Firebug to look for the message. Here are a few interesting findings from:

http://HOSTNAME/user/feat-firewall-port-forward-edit.asp

var RemoteManagementPortsCgiBase = “8080,8080,1\|8181,8181,1\|2323,2323,1\|22,22,1\|”;

msg += “Public Port Range conflict with Remote Management Ports.\n”;

if (msg.length > 1)
{
alert(msg);
return false;
}
return true;
}

If you even a little bit of javascript (or simple computer programming for that matter), the solution is clear…. if the ‘msg’ value is empty you will not see the alert or be prevented from making the change you desire.

Lesson to be learned by the Comcast developers (or most likely = subcontractors), always validate submitted form data in your application code, NEVER rely upon javascript alone to verify user entered data!

I also find it interesting that they are also preventing 8080, 8081 and 2323… perhaps that’s their other back doors in these gateways for their access. The same approach should work for those ports if you need it!

Free Router Firmware Upgrades

I’ve been using an old Linksys WRT-54G (version 2.0) for years, while Linksys released a few firmware updates over the years, none of them really added any new functionality. Thankfully, they had released the source code to the open-source community and several excellent releases have been made available.

Additions such as real-time monitoring/graphing, boosting wireless transmitter power, QoS (Quality of Service) and WOL (Wake-on-LAN) have been added making the router and network much more useful and valuable.

The most prominent versions are:

NOTE: There are several branches on both of these, you can read more at their respective websites.

I was easily able to update from the Linksys firmware (4.21.1) to Tomato 1.25 in only a few minutes, it was even capable of saving my existing configuration making the transition that much easier!

Happy Networking