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DNS Report - issues with IPv6

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URL: https://forums.webwiz.net/forum_posts.asp?TID=31546
Printed Date: 28 March 2026 at 9:18am
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Topic: DNS Report - issues with IPv6

Posted By: jonatkins
Subject: DNS Report - issues with IPv6
Date Posted: 30 May 2018 at 11:28am

It's nice to see an IPv6-enabled DNS report tool, but I've found an issue when testing some domains.

For example, my ISPs domain has some unexpected errors

https://network-tools.webwiz.net/dns-report.htm?domain=aa%2Enet%2Euk&mail=false&IPv6=true

As far as I can see, the problem relates to incorrect shortening of addresses. Specifically, more than one run of zeros are replaced with double colon.

e.g.

primary-dns.co.uk
[2001:8b0::30::51bb:1e29 - No Glue] [TTL: 172800 - 2 Days]
secondary-dns.co.uk
[2001:8b0::81::51bb:5120 - No Glue] [TTL: 172800 - 2 Days]

Note the double-colons both after 2001:8b0, and also after the 30 or 81. These are not valid, as multiple double-colons are ambiguous in IPv6 addresses.

This is more than just a display error - these incorrect addresses appear to be passed into later tests, making them fail.

Replies:

Posted By: WebWiz-Bruce
Date Posted: 30 May 2018 at 12:12pm

Thank you for reporting this issue.

It looks like the IPv6 address is not being compressed correctly as you are only allowed 1 set of colons in the IPv6 address.

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Posted By: WebWiz-Bruce
Date Posted: 30 May 2018 at 12:31pm

The IPv6 address that should have been returned is;

2001:8b0:0:30::18

This is unusual as you have 2001:8b0:0:30 which if there was not the double colon at the end would be compressed to 2001:8b0::30

It seems that the IPworks DNS component that we are using in the test to do the DNS lookup is returning the incorrect IPv6 address.

We will need to report this to vendors of the IPworks DNS component as a bug.

Other IPv6 address work correctly, it seems that the format of your ISP's IPv6 addresses is causing the issue.

Posted By: jonatkins
Date Posted: 30 May 2018 at 3:34pm

Thanks for the quick response and looking into this. Hopefully IPWorks DNS gets fixed soon.

Posted By: WebWiz-Bruce
Date Posted: 31 May 2018 at 2:46pm

/n softwareg the developers of IP*Works! have confirmed this as a bug in their IP*Works! DNS component.

Unfortunately in order to get a fix for the bug they want us to subscribe to their Red Carpet Subscription at a cost of $1,599 per year!

We are waiting to hear back from them to see if their are any other options as it is hard to justify $1,599 per year for the free tools.

The other option is to rewrite the code to use a socket instead to communicate with the DNS server, but this would take time to develop the new code.

Posted By: jonatkins
Date Posted: 31 May 2018 at 2:54pm

Ouch! Yeah - can't see it be worth that much. Well, now they know it's a bug perhaps a fix will eventually get into the free version.

I can't see many people being hit by this issue, so may not be worth the effort to rewrite the code for this.

One suggestion I do have - just *detect* these badly formatted IPv6 addresses, and skip using them in further tests. Yes, it doesn't actually fix the problem, but at least it would prevent confusion for the rare case it's an issue.

Posted By: WebWiz-Bruce
Date Posted: 31 May 2018 at 3:39pm

The other option is to use regular expressions to check the returned result for multiple sets of colons :: and then just pad out the sets of colons with :0: leaving just the last set.

The developers of IP*Works! have just come back with a much better price so are hopeful that will be able to upgrade to a version that does not suffer from the bug.

They do not do a free version of IP*Works! so are stuck with the paid version.

Posted By: WebWiz-Bruce
Date Posted: 01 June 2018 at 10:32am

We have now updated to the latest version of IP*Works!, and while it does return the double colons in the wrong place the IPv6 address is valid enough for the test to complete;

https://network-tools.webwiz.net/dns-report.htm?domain=aa%2Enet%2Euk&mail=false&IPv6=true" rel="nofollow - https://network-tools.webwiz.net/dns-report.htm?domain=aa%2Enet%2Euk&mail=false&IPv6=true

Just of out interest the address you are testing 'aa.net.uk' belongs to the ISP that we use for mobile data SIM's as they give a static IP address.