DNS
DNS uses TCP and UDP.
- UDP, for user queries
- TCP
- Zone transfers (how DNS replicates it’s records to other DNS boxes)
- Requests exceed 512 bytes
- DNSSEC/EDNS
DNS Resource Records
| RR | Description |
|---|---|
| A | v4 IP Address |
| AAAA | v6 IP Address |
| CNAME | Alias or nickname. Secondary Name |
| MX | Email server |
| NS | DNS Server |
| PTR | Reverse Mapping of an IP. Used to find the host that “owns” the IP |
| SOA | Start of Authority. Which DNS server is authorative for the zone. |
DHCP & DNS Placement
Always in groups of at least two, this is a HA service.
Each module should have it’s own set of DHCP and DNS nodes.
| Location | DHCP | DNS |
|---|---|---|
| Enterprise / Campus / DC | Yes | Internal DNS |
| Enterprise / Remote / Branch | Yes | Internal DNS |
| Enterprise / Remote / DC | — | Internal and External DNS |
| Enterprise / Edge / DMZ | — | External DNS |
| Enterprise / Edge / WAN | — | — |
| Enterprise / Edge / VPN | — | — |
| SP / Edge | — | External DNS |