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richwales's profile



3 Messages

Friday, June 10th, 2016 12:00 PM

Reverse DNS for static IPv6?

Is it possible to get reverse DNS for a static IPv6 prefix?


I live on the San Francisco Peninsula.  I have Business Class service, with five static IPv4 addresses and reverse DNS.  This service works just fine for me. Smiley Happy


I can see that I also have IPv6.  However, I can't find any information online about (1) whether my 64-bit IPv6 prefix is static or dynamic, or (2) how to set reverse DNS (or have Comcast set it up for me) if my IPv6 prefix does happen to be static.


So I phoned Comcast Business tech support just now -- and after initially being told in error that I couldn't have both IPv4 and IPv6 (I could supposedly have only one or the other, but not both), I got to a supervisor who told me that I do in fact have both IPv4 and IPv6, and that my IPv6 prefix is static. Smiley Happy


HOWEVER, this supervisor then told me that even though my IPv6 prefix is statically allocated, I could NOT get reverse DNS set up for it.  Comcast (according to this supervisor) has not announced any plans to offer reverse DNS support for IPv6. Smiley Sad


I'm not fully confident that support gave me correct info -- as I said, the first person I spoke to claimed it wasn't possible to have both IPv4 and IPv6 -- so I'd like to hear from anyone else who either has reverse DNS for their static IPv6, or else has been told that this is not available.  Also, is there any way for me to independently verify that the support supervisor was correct when she said my IPv6 address allocation is static?

Problem solver


326 Messages

8 years ago

Your IPv6 is NOT static.  If you turn OFF your modem for a few days and then turn it back on you will almost certainly get a different IPv6 address.


In some markets Comcast is trialing static IPv6.  You can call Comcast and ask to be transferred to business sales and then when you are talking to a salesman, tell him you want it and have him ask to find out when your area is getting static IPv6.


Comcast assigns Ipv6 via DHCP.  Thus there is a lifetime that your modem has the IPv6.  If your modem renews at the end of that lifetime, then you will get the renewal approved and you will continue to have the same IPv6 number.   If the end of the lifetime comes and your modem is off playing with itself or is turned off or whatever, then the lease expires and your IPv6 number is then free to be assigned to someone else.  The longer that your modem waits after this point before asking for a renewal, the more chance you won't get the same Pv6 address back.

Frequent Contributor


36 Messages

8 years ago

That area has static IPv6 now.  I wish there was a web tool for reverse DNS.