seanism DOT com Random thoughts from the world of seanism


Comcast DNS Helper

A client of mine mentioned he wasn't able to access his mapped drives over the VPN.  I remotely connected to his PC and noticed if I pinged hostname.domain.local it resolves to  I confirmed he was connected to the VPN and I could ping the IP of the PC directly.  I did a quick lookup of that IP address and it turns out its owned by Comcast.  Comcast's DNS Helper service was to blame.  They were resolving all failed hostnames to their IP address rather then letting it fail and allowing his companies DNS server to resolve it correctly.

To fix this you have 2 options:

  1. Opt-Out of Comcast's DNS Helper service
  2. Switch to a public DNS service like OpenDNS or Google's DNS servers

Right now Comcast has this enabled by default for all customers with dynamically assigned IP addresses.  Business customers are not affected.

Below is an article on the topic that is a great read.


Connecting to a Windows PPTP VPN from Ubuntu 10.04

If you'd like to connect to a Windows PPTP VPN here is a howto to make it happen.

You need to have Ubuntu 10.04 if not you need to apt-get some packages that are not installed by default.

  1. Click 'System' -> 'Preferences' -> 'Network Connections'
  2. Click the 'VPN' tab
  3. Leave 'Point-to-Point Tunneling Protocol (PPTP)' selected
  4. 'Click Create...'
  5. Type in a connection name and check the box below it if you'd like the connection to connect automatically
  6. For 'Gateway' enter in the VPN hostname or IP IE or x.x.x.x
  7. For the username type in DOMAINusername where DOMAIN is your Windows domain name and username is.... your username
  8. Type in your password and leave the 'NT Domain:' box empty
  9. Click 'Advanced...'
  10. Check 'Use Point-to-Point encryption (MPPE) and leave 'Security' on 'All Available (Default)'
  11. Check 'Allow BSD data compression'
  12. Check 'Allow Deflate data compression'
  13. Check 'Use TCP header compression'
  14. Leave 'Allow stateful encryption' and 'Send PPP echo packets' unchecked
  15. Click 'OK'

Now this will send all your network traffic over the VPN. If you'd like to still be able to use your local connection you need to click the 'IPv4 Settings' tab, click 'Routes...' and check 'Use this connection only for resources on its network'. Enabling this can be a security risk so you should talk to your IT administrator first before enabling it. That option is called split tunneling.

Click 'Apply'

Now to connect left click your network icon in the panel on the top right and hover over 'VPN Connections' and left click the connection you just created.

I'm not on a connection that allows me to do further testing but when I can I'll update this with more information.

For earlier versions of Ubuntu use the following KB article to help you install the necessary programs.