GUIDEServer Management

Server Networking — IPs, DNS, Reverse DNS

5 min read

Proper networking configuration is essential for making your server accessible on the internet, hosting websites, sending email, and running applications. This guide explains how IP addresses, DNS, and reverse DNS work together on your Data Mammoth server and how to configure them correctly.

Understanding Your Server's IP Address

Every Data Mammoth server is assigned at least one public IPv4 address when it is provisioned. You can find your IP address in several places:

Server dashboard — Displayed prominently on the overview panel.
Server list — Shown next to each server name.
Provisioning email — Included in the welcome email sent when your server is created.

IPv4 and IPv6

IPv4 — The traditional IP address format (e.g., 203.0.113.10). Every server receives at least one IPv4 address.
IPv6 — The newer, longer format (e.g., 2001:0db8:85a3::8a2e:0370:7334). If available, IPv6 addresses are assigned automatically and can be used alongside IPv4.

Viewing IP Configuration from the Command Line

# Show all network interfaces and IP addresses
ip addr show
Show only IPv4 addresses
ip -4 addr show
Show only IPv6 addresses
ip -6 addr show

DNS — Domain Name System

DNS translates human-readable domain names (like example.com) into IP addresses that computers use to communicate. To point a domain to your server, you need to configure DNS records.

Common DNS Record Types

Record Type	Purpose	Example
A	Maps a domain to an IPv4 address	`example.com → 203.0.113.10`
AAAA	Maps a domain to an IPv6 address	`example.com → 2001:0db8::1`
CNAME	Creates an alias pointing to another domain	`www.example.com → example.com`
MX	Specifies mail servers for the domain	`example.com → mail.example.com`
TXT	Stores text data (SPF, DKIM, verification)	`example.com → "v=spf1 ..."`
NS	Specifies the authoritative name servers	`example.com → ns1.example.com`

Setting Up DNS for Your Server

To point your domain to your Data Mammoth server:

Log in to your domain registrar (where you purchased the domain).

Navigate to DNS Management or Name Servers settings.

Create an A record:

- Name/Host: @ (for the root domain) or a subdomain (e.g., www) - Type: A - Value: Your server's IPv4 address (e.g., 203.0.113.10) - TTL: 3600 (1 hour) or as recommended

If applicable, create a CNAME record for www:

- Name/Host: www - Type: CNAME - Value: example.com

Save your changes.

DNS changes can take anywhere from a few minutes to 48 hours to propagate globally, though most updates take effect within 1 to 4 hours.

Verifying DNS Records

Use these commands to verify your DNS configuration:

# Check A record
dig example.com A +short
Check AAAA record
dig example.com AAAA +short
Check all records for a domain
dig example.com ANY
Alternative using nslookup
nslookup example.com

Reverse DNS (PTR Records)

Reverse DNS maps an IP address back to a domain name — the opposite of what regular DNS does. PTR (pointer) records are essential for:

Email deliverability — Many mail servers reject messages from IPs without valid reverse DNS.
Server identification — Helps identify servers in logs and traceroutes.
Security compliance — Some applications and services require matching forward and reverse DNS.

How Reverse DNS Works

When a mail server receives an email from 203.0.113.10, it performs a reverse DNS lookup to check if the IP resolves to a hostname. If it resolves to mail.example.com, the mail server then performs a forward lookup on mail.example.com to verify it points back to 203.0.113.10. This forward-confirmed reverse DNS (FCrDNS) builds trust.

Setting Up Reverse DNS

Navigate to your server's Networking tab.

Find the Reverse DNS or PTR section.

Click Edit next to your IP address.

Enter the fully qualified domain name (e.g., mail.example.com).

Click Save.

Important: Before setting up reverse DNS, make sure a corresponding forward DNS A record exists and points to the same IP address. Reverse DNS will not work correctly without a matching forward record.

Verifying Reverse DNS

# Check PTR record for an IP
dig -x 203.0.113.10 +short
Alternative
host 203.0.113.10

The output should show your configured hostname.

Network Troubleshooting

Cannot Reach Server by IP

Check the server status in your dashboard — ensure it is running.

Verify the IP address: ip addr show

Check if the firewall is blocking traffic: sudo iptables -L -n

Test connectivity from the server: ping -c 4 8.8.8.8

DNS Not Resolving

If your domain does not resolve to your server:

Verify the A record with dig example.com A +short.

Check that DNS propagation is complete (allow up to 48 hours for new domains).

Ensure the correct IP is set in the A record.

See DNS Not Resolving — Common Fixes for detailed troubleshooting.

Email Being Rejected

If email from your server is being rejected:

Verify reverse DNS is configured correctly.

Check that forward DNS matches the PTR record.

Ensure SPF, DKIM, and DMARC records are set up.

See Email Not Sending from Server.

What to Do Next

Adding Additional IP Addresses — Request and configure extra IPs.
Changing Your Server Hostname — Set a hostname that matches your DNS.
SSL/TLS Certificates — Setup & Renewal — Secure your domain with HTTPS.
Email Not Sending from Server — Troubleshoot email delivery issues.

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