Chart: The Pitfalls of Microsoft DNS

BY Ben Ball

Every IT organization on the planet wants to get by with the network infrastructure they have.  Change is hard, and inherently risky.  There has to be a pretty big reason to go in a different direction.

The Domain Name System (DNS) is no different.  Most organizations start off with a simple, out of the box Microsoft DNS solution.  For the number of DNS zones and DNS servers in most small networks, it probably works fine.  It's the default choice for Active Directory, so everything seems natural.  

Yet there will inevitably come a time when the cost of free network infrastructure management is simply too high.  As organizations scale, as strategic initiatives introduce more complexity, as workloads grow, all of the downsides of a Microsoft DNS infrastructure begin to show themselves. 

Suddenly, the network seems fragile - errors and configuration issues in DNS entries often lead to downtime.  Suddenly, the number of DNS queries grows dramatically and you have limited visibility into what's happening on the network - either your external DNS or your internal DNS.  Suddenly, even the "overlay" solutions you put in place start to fail.  It's at these times that all those Microsoft DNS issues start to cascade.

What are the symptoms of a system weighed down by Microsoft DNS?  We put this handy chart together to demonstrate some of the operational challenges we see with customers of ours who are getting ready to migrate away from Microsoft DNS.

DNS ISSUES CAUSED BY IMPACT
Hidden zones Inconsistent query paths Traveling users suffer loss of access to important services
Delayed DNS zone synchronization Setting up slaves but failing to enable notifications for those slaves Some internal locations or customers can see the modified/new record, and others are still receiving the wrong answer
Delegations reference missing glue records Misconfiguration + stale data + decommissioned hardware Service outages caused by failure to update all instances of a delegation target
Stale DDNS Host and PTR records Misconfigured, broken or unused MS DNS scavenging and allowing company-wide DNS self-registration Visual inspection becomes impossible because of huge, cluttered list of stale DNS records
DHCP ISSUES CAUSED BY IMPACT
DHCP reservations with invalid MAC addresses Bad data entry Inaccurate IP address data. Confusion as to why device has the wrong IP address or doesn’t exist anymore
Fake DHCP reservations Manually misconfigured DHCP ranges (aka “Poor man’s IPAM solution) Inaccurate IP address data. Inability to know if it's safe to allocate the IP address
Unreachable gateway Bad data entry DHCP outages
Conflicting scopes between servers DHCP services moved without cleanup or creation of backup server IP address conflicts caused by dueling DHCP servers, DHCP reservations and DHCP option changes don't take effect or stop working, DHCP pool exhaustion
IPAM ISSUES CAUSED BY IMPACT
IPAM networks conflicts with DHCP data Bad data entry Misconfiguration of routing tables, overlapping network segments inaccessible by DHCP clients due to netmask errors
DNS data references unknown private networks No single source of truth - each group or BU tracks networks in a different way Impossible to properly provision networks and wasted IP space, network equipment, and under-utilized servers
Static and DHCP-reserved IP addresses within active DHCP scopes Bad practice from MS requirement in early versions of their DHCP service Unintentional reduction in DHCP pool size, increased risk of surprise DHCP pool exhaustion, risk of DHCP conflicts
Stale IPAM data and lack of input restrictions Legacy networks from sold-off divisions or old work sites Unnecessary purchase of additional network hardware, vulnerable services present on the production network

Do any of these sound familiar?  Read more about the high cost of free DNS with our "Cost of Free" eBook.  We'd love to talk about how to replace Microsoft DNS on your network and get you the functionality you require from an enterprise level DDI solution.  Leave feedback on our contact us page and we'll be in touch.

Ben Ball

Ben Ball is the Director of Strategy and Content Marketing at BlueCat. Ben served for ten years as a Federal employee, with three tours as a Foreign Service Officer (Saudi Arabia, Turkey, Jordan), and five years at the Department of Homeland Security, where he focused on immigration issues. A graduate of the Fletcher School of Law and Diplomacy and Pitzer College, Ben lives in the San Francisco Bay Area.

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