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DNS Problem with Comcast Nameservers

This issue was reported today by the Cisco Small Business Support Center.  A new OnPlus subscriber was attempting to signup for service.  The user's browser was unable to resolve the OnPlus Portal at www.cisco-onplus.com .  Other sites were resolving correctly from the browser, however.

Further investigation revealed that the subscriber is a Comcast customer and using Comcast's DNS servers.  Using Comcast DNS tools found at

http://dns.comcast.net/index.php we were able to verify Comcast nameservers are not resolving cisco-onplus.com addresses.  Other publicly available DNS servers are working as expected.

If you are experiencing this issue a workaround is available.  It is possible to manually configure the client computer to use other publicly available DNS services.  We verified that Google name servers (8.8.8.8 and 8.8.4.4) are correctly resolving cisco-onplus.com .  The method for manually configuring DNS servers varies based on the client OS.  For example, Windows 7 users accomplish this by opening the Network and Sharing Center and choosing the Change Adapter Settings option.

We are currently working to determine Root Cause and will update this discussion in due course. 

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DNS Problem with Comcast Nameservers

Status Update:

The Root Cause was identified and a patch applied to OnPlus nameservers on Friday Jan 20.  We verified that ComCast nameservers are now accepting responses from OnPlus nameservers. 

If you implemented the manual workaround described in this post, it is now safe to remove the workaround and return to the normally provisioned DNS servers.

Analysis:

The root cause was determined to be misconfigured nameservers within the OnPlus network.  The nameservers were not responding as Authoritative for zones in the OnPlus network including cisco-onplus.com.  For security reasons certain nameservers insist on an Authoritative response.  Comcast nameservers fall into this group.  Modifying the OnPlus nameservers' configurations resolved the issue.

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