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Many threads on this forum have discussed issues with ATTBI DNS performance and Windows XP/2000. These operating systems have a feature, called "DNS Service", that manipulates the list of DNS servers it is aware of so that the fastest-responding servers are consulted first. You can see the following two URLs for reference on this behavior:


The ATTBI network had been providing four DNS server addresses via the DHCP lease. The first two of these were virtual IPs for our production DNS servers. These production DNS servers are configured to resolve all public Internet addresses as well as internal ATTBI addresses.

The second two DNS server addresses are the addresses of the SAS (Service Activation System) DNS servers. We distribute these addresses to PCs in support of new customer registration. The SAS DNS servers can only resolve addresses that are used for registration and won't resolve anything else. Since the SAS servers are fast, Windows XP and Windows 2000's DNS Services would quickly choose one of them as the most responsive DNS server, and consult it rather than the ones that had more meaningful information. Users would then find that they could not get to any address on the Internet. If they had tried to access a public Internet site via its IP address, it would have worked. Some users attributed this behavior to a network connectivity failure when in fact, nothing had failed - the OS had simply latched on to a DNS that couldn't resolve public addresses.

Many users found that releasing/renewing their IP Lease, or flushing the DNS cache would cure this problem, at least for a few minutes. Another solution was to stop the DNS Service (from the Control Panel/Services applet). None of these was a permanent fix. While stopping the DNS Service did prevent the OS from permanently latching onto the SAS DNS servers, it would still occasionally consult them resulting in browser errors for users.

We have implemented two changes to correct this situation. First, we have improved the performance of the production DNSs so that Windows XP and Windows 2000 will not time-out on them. Second, we have redesigned our registration process such that the SAS DNSs are no longer required. Therefore, effective 12/20/01, our DHCP servers will no longer offer the SAS DNS server addresses - only the two virtual IPs of the production DNS servers will be distributed.

If you have manually adjusted your system to point to specific DNS IP addresses, either ATTBI DNS or 3rd party DNS, we advise you to restore your DNS settings so that you can get your DNS addresses via DHCP. We also advise you to restart your Windows XP or Windows 2000 DNS Service. After you have adjusted your system, you should release and renew your IP address (or more simply, just reboot your system) to fetch the new DNS address list from the server.

AT&T Technical Support

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