Root Hints in DNS: Understanding DNS Zones

Study Notes

DNS Revision

Global distribution database that resolves Fully Qualified Domain Names to IP Addresses and IP addresses to host names
Locates domain controllers and global catalog servers
Used in mail server during email delivery
IP Addresses for DNS root Servers:
- Named authorities servers in the DNS root zone
- Ask root servers for DNS if unknown

DNS Zones

DNS Zone Types:
- Primary Zone: Writeable copy of DNS Zone (records only)
- Secondary Zone: Read-only copy of DNS from another DNS server via Zone Transfer
- Stub Zone: Read-only subset copy of DNS zone - list of zone authoritative DNS servers
- AD Integrated Zone: DNS Server installed on Domain Controllers
  - Data in AD DS rather than zone files
  - Primary zone or Stub Zone
  - Security + Availability

DNS Zone Storage

Text:
- Zone data on txt file on server
Active Directory Integrated:
- Zone data on domain controllers with multi-master replication

DNS Zone Focus

Forward Lookup Zone:
- Resolve FQDNs to IP Addresses
- A, MX, SRV, NS, SOA, CNAME
Reverse Lookup Zone:
- Resolve IP to Host names
- PTR

DNS Queries

DNS Clients and Servers initiate queries
Recursive or iterative
- Recursive: Gives required result or returns error
- Iterative: Gives best answer it can, often a referral to another server

Forwarders and Conditional Forwarders

Forwarders:
- Queries that cannot be resolved by DNS to be forwarded to:
  - ISP's DNS server
  - Head office DNS Server
  - Parent Domain's DNS Server
Conditional Forwarders:
- All queries for this domain will be forwarded directly to this domain's DNS server

DNS Security and Troubleshooting

DNSSec: private/public key for identity and encrypt DNS traffic
Split-Brain DNS: Prevents external users from gleaning details of network
- Internal DNS: Dynamic, full copy of Zone
- External DNS: Manual, only small number of records eg www
Resolve-DnsName, Nslookup, DNSCmd, Ipconfig, Ping for troubleshooting
DNS Database Clean and Accurate:
- Identify client DNS server w/ nslookup or powershell cmdlet ResolveDnsName
- Communicate via ping
- Use DNS management console or nslookup to verify records
- TTL: Time to live, how long DNS record will remain valid
- Aging: Occurs when records that have been inserted into DNS server reach expiration and are removed
- Scavenging: Performs DNS server resource record grooming for old records in DNS

DNS Zone Delegation

DNS subdomain is child domain
- Part of parent domain and has same domain suffix as parent domain
- Can be stored in different DNS server than DNS server with parent
GlobalNames Zone:
- Allow single label names to be resolved in multiple DNS domain environments

DHCP Revision

DHCP Configuration:
- DHCP clients automatically given IP Address
- Correct config ensured, reduces network problems
- Windows Server 2016 has IPv6 for DHCP Server
Scope: One subnet > 1 scope
Exclusion range: Static Ips Reserved IP
DHCP Relay Agent:
- Supports DHCP clients on remote subnets
- Local to DHCP clients it supports
- Often configured at routers

DHCP Advanced Scopes

Superscopes: Support multiple logical networks on single physical network
- Ease transitioning to new IP scheme
Multicast scopes: Support apps that need simultaneous communication with multiple clients
Split scopes: 2 DHCP servers
- Ensure no overlapping, each DHCP is configured with different subset of IP Addresses
- Can setup Failover with same subset of IP addresses instead

IPAM

IP Address Management
Implement IP Address management
Deploy, monitor and administer organization IP infrastructure
Manage and maintain all aspects of DNS and DHCP servers

Description

Test your knowledge on DNS root hints, global distribution database, DNS zones, and zone types. Topics covered include resolving domain names to IP addresses, locating domain controllers, and understanding primary DNS zones.